1 of 60 REV: 011706
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FEATURES
Complete DS1/ISDN-PRI Transceiver
Functionality
Line Interface Can Handle Both Long- and
Short-Haul Trunks
32-Bit or 128-Bit Jitter Attenuator
Generates DSX-1 and CSU Line Build-Outs
Frames to D4, ESF, and SLC-96R Formats
Dual On-Board Two-Frame Elastic Store Slip
Buffers that Connect to Backplanes Up to
8.192MHz
8-Bit Parallel Control Port That can be Used
on Either Multiplexed or Nonmultiplexed
Buses
Extracts and Inserts Robbed-Bit Signaling
Detects and Generates Yellow and Blue
Alarms
Programmable Output Clocks for Fractional
T1
Fully Independent Transmit and Receive
Functionality
On-Board FDL Support Circuitry
Generates and Detects CSU Loop Codes
Contains ANSI One’s Density Monitor and
Enforcer
Large Path and Line Error Counters Including
BPV, CV, CRC6, and Framing Bit Errors
Pin Compatible with DS2153Q E1 Single-
Chip Transceiver
5V Supply; Low-Power CMOS
PIN CONFIGURATION
ORDERING INFORMATION
PART TEMP
RANGE
PIN-
PACKAGE
DS2151Q 0°C to +70°C 44 PLCC
DS2151Q+ 0°C to +70°C 44 PLCC
DS2151QN -40°C to +85°C 44 PLCC
DS2151QN+ -40°C to +85°C 44 PLCC
+Denotes lead-free/RoHS-compliant package.
DS2151Q
T1 Single-Chip Transceive
r
www.maxim-ic.com
Dallas
DS2151Q
T1SCT
ELASTIC
STORES
FRAMER
LONG & SHORT
HAUL LINE
INTERFACE
PARALLEL CONTROL
PORT
ACTUAL SIZE OF 44-PIN PLCC
FUNCTIONAL BLOCKS
ALE(AS)
WR (R/W)
RLIN
K
RLCL
K
DVSS
RCL
K
RCHCL
K
RSE
R
RSYNC
RLOS/LOTC
SYSCL
K
TSER
TCLK
DVDD
TSYNC
TLINK
TLCLK
TCHBLK
TRING
TVDD
TVSS
TTIP
RCHBL
K
ACLKI
BTS
RTIP
RRING
RVDD
RVSS
XTAL1
XTAL2
INT
1
INT
2
C
S
R
D(DS)
A
D7
A
D6
A
D5
A
D4
A
D3
A
D2
A
D1
A
D0
TCHCLK
1
2
3
4
5
6
44
43
42
41
40
7
17
16
15
14
13
12
11
10
9
8
18
19
20
21
22
23
24
25
26
27
28
39
38
37
36
35
34
33
32
31
30
29
DS2151Q
PLCC
DS2151Q
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TABLE OF CONTENTS
1 DETAILED DESCRIPTION....................................................................................................4
1.1 INTRODUCTION................................................................................................................................4
2 PIN DESCRIPTION................................................................................................................6
2.1 DS2151Q REGISTER MAP...............................................................................................................8
3 PARALLEL PORT .................................................................................................................9
4 CONTROL REGISTERS......................................................................................................10
4.1 LOCAL LOOPBACK .........................................................................................................................15
4.2 REMOTE LOOPBACK ......................................................................................................................15
4.3 PAYLOAD LOOPBACK.....................................................................................................................15
4.4 FRAMER LOOPBACK ......................................................................................................................15
4.5 LOOP CODE GENERATION .............................................................................................................18
4.6 PULSE DENSITY ENFORCER...........................................................................................................18
4.7 POWER-UP SEQUENCE .................................................................................................................18
5 STATUS AND INFORMATION REGISTERS ......................................................................19
5.1 LOOP UP/DOWN CODE DETECTION................................................................................................23
6 ERROR COUNT REGISTERS.............................................................................................27
6.1 LINE CODE VIOLATION COUNT REGISTER (LCVCR) .......................................................................27
6.2 PATH CODE VIOLATION COUNT REGISTER (PCVCR)......................................................................28
6.3 MULTIFRAMES OUT OF SYNC COUNT REGISTER (MOSCR) ............................................................29
7 FDL/FS EXTRACTION AND INSERTION ...........................................................................30
7.1 RECEIVE SECTION.........................................................................................................................30
7.2 TRANSMIT SECTION.......................................................................................................................31
8 SIGNALING OPERATION...................................................................................................32
9 TRANSMIT TRANSPARENCY AND IDLE REGISTERS ....................................................34
10 CLOCK BLOCKING REGISTERS....................................................................................36
11 ELASTIC STORES OPERATION.....................................................................................37
11.1 RECEIVE SIDE............................................................................................................................37
11.2 TRANSMIT SIDE..........................................................................................................................37
11.3 MINIMUM DELAY SYNCHRONOUS SYSCLK MODE.......................................................................37
12 RECEIVE MARK REGISTERS.........................................................................................38
13 LINE INTERFACE FUNCTIONS.......................................................................................39
13.1 RECEIVE CLOCK AND DATA RECOVERY.......................................................................................40
13.2 TRANSMIT WAVESHAPING AND LINE DRIVING ..............................................................................41
13.3 JITTER ATTENUATOR.................................................................................................................. 42
14 TIMING DIAGRAMS .........................................................................................................46
15 DC CHARACTERISTICS..................................................................................................52
16 AC CHARACTERISTICS..................................................................................................53
17 PACKAGE INFORMATION..............................................................................................60
17.1 44-PIN PLCC (56-G4003-001)..................................................................................................60
DS2151Q
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LIST OF FIGURES
Figure 1-1. DS2151Q Block Diagram .........................................................................................................5
Figure 13-1. External Analog Connections...............................................................................................43
Figure 13-2. Jitter Tolerance ....................................................................................................................43
Figure 13-3. Transmit Waveform Template..............................................................................................44
Figure 13-4. Jitter Attenuation ..................................................................................................................45
Figure 14-1. Receive Side D4 Timing.......................................................................................................46
Figure 14-2. Receive Side ESF Timing ....................................................................................................46
Figure 14-3. Receive Side Boundary Timing with Elastic Store(s) Disabled ............................................47
Figure 14-4. 1.544MHz Boundary Timing with Elastic Store(s) Enabled..................................................47
Figure 14-5. 2.048MHz Boundary Timing with Elastic Store(s) Enabled..................................................48
Figure 14-6. Transmit Side D4 Timing......................................................................................................48
Figure 14-7. Transmit Side ESF Timing ...................................................................................................49
Figure 14-8. Transmit Side Boundary Timing with Elastic Store(s) Disabled ...........................................50
Figure 14-9. Transmit Data Flow ..............................................................................................................51
Figure 16-1. Intel Bus Read AC Timing....................................................................................................54
Figure 16-2. Intel Bus Write AC Timing ....................................................................................................54
Figure 16-3. Motorola Bus AC Timing ......................................................................................................55
Figure 16-4. Receive Side AC Timing ......................................................................................................57
Figure 16-5. Transmit Side AC Timing .....................................................................................................59
LIST OF TABLES
Table 4-1. Output Pin Test Modes............................................................................................................13
Table 5-1. Receive T1 Level Indication ....................................................................................................21
Table 5-2. Alarm Set and Clear Criteria ...................................................................................................23
Table 6-1. Line Code Violation Counting Arrangements ..........................................................................27
Table 6-2. Path Code Violation Counting Arrangements..........................................................................28
Table 6-3. Multiframes Out of Sync Counting Arrangements ................................................................... 29
Table 13-1. Source of RCLK Upon RCL...................................................................................................40
Table 13-2. LBO Select in LICR ...............................................................................................................41
Table 13-3. Transformer Specifications....................................................................................................41
Table 13-4. Crystal Selection Guidelines .................................................................................................42
Table 15-1. Recommended DC Characteristics .......................................................................................52
Table 15-2. Capacitance ..........................................................................................................................52
Table 15-3. DC Characteristics ................................................................................................................52
Table 16-1. AC Characteristics—Parallel Port .........................................................................................53
Table 16-2. AC Characteristics—Receive Side........................................................................................56
Table 16-3. AC Characteristics—Transmit Side.......................................................................................58
DS2151Q
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1 DETAILED DESCRIPTION
The DS2151Q T1 single-chip transceiver (SCT) contains all the necessary functions for connection to T1
lines whether they be DS-1 long haul or DSX-1 short haul. The clock recovery circuitry automatically
adjusts to T1 lines from 0 feet to over 6000 feet in length. The device can generate both DSX-1 line
build-outs as well as CSU build-outs of -7.5dB, -15dB, and -22.5dB. The on-board jitter attenuator
(selectable to either 32 bits or 128 bits) can be placed in either the transmit or receive data paths. The
framer locates the frame and multiframe boundaries and monitors the data stream for alarms. It is also
used for extracting and inserting robbed-bit signaling data and FDL data. The device contains a set of 64
8-bit internal registers that the user can access to control the operation of the unit. Quick access via the
parallel control port allows a single micro to handle many T1 lines. The device fully meets all of the latest
T1 specifications including ANSI T1.403-199X, AT&T TR 62411 (12-90), and ITU G.703, G.704,
G.706, G.823, and I.431.
1.1 Introduction
The analog AMI waveform off of the T1 line is transformer coupled into the RRING and RTIP pins of
the DS2151Q. The device recovers clock and data from the analog signal and passes it through the jitter
attenuation mux to the receive side framer where the digital serial stream is analyzed to locate the framing
pattern. If needed, the receive side elastic store can be enabled in order to absorb the phase and frequency
differences between the recovered T1 data stream and an asynchronous backplane clock which is
provided at the SYSCLK input.
The transmit side of the DS2151Q is totally independent from the receive side in both the clock
requirements and characteristics. Data can be either provided directly to the transmit formatter or via an
elastic store. The transmit formatter will provide the necessary data overhead for T1 transmission. Once
the data stream has been prepared for transmission, it is sent via the jitter attenuation mux to the
waveshaping and line driver functions. The DS2151Q will drive the T1 line from the TTIP and TRING
pins via a coupling transformer.
DS2151Q
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Figure 1-1. DS2151Q Block Diagram
DS2151Q
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2 PIN DESCRIPTION
PIN NAME TYPE FUNCTION
1–4,
41–44
AD4–AD7,
AD0–AD3 I/O Address/Data Bus. An 8-bit multiplexed address/data bus.
5 RD(DS) I Active-Low Read Input (Data Strobe)
6 CS I Active-Low Chip Select. Must be low to read or write the port.
7 ALE(AS) I
Address Latch Enable (Address Strobe). A positive going edge serves to
demultiplex the bus.
8 WR(R/W) I Active-Low Write Input (Read/Write)
9 RLINK O
Receive Link Data. Updated with either FDL data (ESF) or Fs bits (D4) or
Z bits (ZBTSI) one RCLK before the start of a frame. See Section 14 for
timing details.
10 RLCLK O
Receive Link Clock. 4kHz or 2kHz (ZBTSI) demand clock for the RLINK
output. See Section 14 for timing details.
11 DVSS — Digital Signal Ground. 0.0V. Should be tied to local ground plane.
12 RCLK O Receive Clock. Recovered 1.544MHz clock.
13 RCHCLK O
Receive Channel Clock. 192kHz clock that pulses high during the LSB of
each channel. Useful for parallel to serial conversion of channel data,
locating Robbed-Bit signaling bits, and for blocking clocks in DDS
applications. See Section 14 for timing details.
14 RSER O
Receive Serial Data. Received NRZ serial data, updated on rising edges of
RCLK or SYSCLK.
15 RSYNC I/O
Receive Sync. An extracted pulse, one RCLK wide, is output at this pin,
which identifies either frame (RCR2.4 = 0) or multiframe boundaries
(RCR2.4 = 1). If set to output frame boundaries, then via RCR2.5, RSYNC
can also be set to output double-wide pulses on signaling frames. If the
elastic store is enabled via the CCR1.2, then this pin can be enabled to be
an input via RCR2.3 at which a frame boundary pulse is applied. See
Section 14 for timing details.
16 RLOS/LOT
C O
Receive Loss of Sync/Loss of Transmit Clock. A dual function output. If
CCR3.5 = 0, will toggle high when the synchronizer is searching for the T1
frame and multiframe; if CCR3.5 = 1, will toggle high if the TCLK pin has
not toggled for 5µs.
17 SYSCLK I
System Clock. 1.544MHz or 2.048MHz clock. Only used when the elastic
store functions are enabled via either CCR1.7 or CCR1.2. Should be tied
low in applications that do not use the elastic store. If tied high for more
than 100µs, will force all output pins (including the parallel port) to tri-
state.
18 RCHBLK O
Receive Channel Block. A user-programmable output that can be forced
high or low during any of the 24 T1 channels. Useful for blocking clocks to
a serial UART or LAPD controller in applications where not all T1
channels are used such as Fractional T1, 384kbps service, 768kbps, or
ISDN-PRI. Also useful for locating individual channels in drop-and-insert
applications. See Section 14 for timing details.
19 ACLKI I
Alternate Clock Input. Upon a receive carrier loss, the clock applied at
this pin (normally 1.544MHz) will be routed to the RCLK pin. If no clock
is routed to this pin, then it should be tied to DVSS via a 1kΩ resistor.
DS2151Q
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PIN NAME TYPE FUNCTION
20 BTS I
Bus Type Select. Strap high to select Motorola bus timing; strap low to select
Intel bus timing. This pin controls the function of the RD(DS), ALE(AS), and
WR(R/W) pins. If BTS = 1, then these pins assume the function listed in
parentheses.
21, 22 RTIP,
RRING — Receive Tip and Ring. Analog inputs for clock recovery circuitry; connects
to a 1:1 transformer (see Section 13 for details).
23 RVDD —
Receive Analog Positive Supply. 5.0V. Should be tied to DVDD and TVDD
pins.
24 RVSS — Receive Signal Ground. 0V. Should be tied to local ground plane.
25, 26 XTAL1,
XTAL2 — Crystal Connections. A pullable 6.176MHz crystal must be applied to these
pins. See Section 13 for crystal specifications.
27 INT1 O Receive Alarm Interrupt 1. Flags host controller during alarm conditions
defined in Status Register 1. Active low, open drain output.
28 INT2 O Receive Alarm Interrupt 2. Flags host controller during conditions defined
in Status Register 2. Active low, open drain output.
29 TTIP —
Transmit Tip. Analog line driver output; connects to a step-up transformer
(see Section 13 for details).
30 TVSS — Transmit Signal Ground. 0V. Should be tied to local ground plane.
31 TVDD —
Transmit Analog Positive Supply. 5.0V. Should be tied to DVDD and
RVDD pins.
32 TRING — Transmit Ring. Analog line driver outputs; connects to a step-up transformer
(see Section 13 for details).
33 TCHBLK O
Transmit Channel Block. A user-programmable output that can be forced
high or low during any of the 24 T1 channels. Useful for blocking clocks to a
serial UART or LAPD controller in applications where not all T1 channels are
used such as Fractional T1, 384kbps service, 768kbps, or ISDN-PRI. Also
useful for locating individual channels in drop-and-insert applications. See
Section 14 for timing details.
34 TLCLK O Transmit Link Clock. 4kHz or 2kHz (ZBTSI) demand clock for the TLINK
input. See Section 14 for timing details.
35 TLINK I
Transmit Link Data. If enabled via TCR1.2, this pin will be sampled during
the F-bit time on the falling edge of TCLK for data insertion into either the
FDL stream (ESF) or the Fs bit position (D4) or the Z-bit position (ZBTSI).
See Section 14 for timing details.
36 TSYNC I/O
Transmit Sync. A pulse at this pin will establish either frame or multiframe
boundaries for the DS2151Q. Via TCR2.2, the DS2151Q can be programmed
to output either a frame or multiframe pulse at this pin. If this pin is set to
output pulses at frame boundaries, it can also be set via TCR2.4 to output
double-wide pulses at signaling frames. See Section 14 for timing details.
37 DVDD — Digital Positive Supply. 5.0V. Should be tied to RVDD and TVDD pins.
38 TCLK I Transmit Clock. 1.544MHz primary clock.
39 TSER I Transmit Serial Data. Transmit NRZ serial data, sampled on the falling edge
of TCLK.
40 TCHCLK O
Transmit Channel Clock. 192kHz clock that pulses high during the LSB of
each channel. Useful for parallel to serial conversion of channel data, locating
robbed-bit signaling bits, and for blocking clocks in DDS applications. See
Section 14 for timing details.
DS2151Q
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2.1 DS2151Q Register Map
ADDRESS R/W REGISTER NAME ADDRESS R/W REGISTER NAME
20 R/W Status Register 1 30 R/W Common Control Register 3
21 R/W Status Register 2 31 R/W Receive Information Register 2
22 R/W Receive Information Register 1 32 R/W Transmit Channel Blocking Register 1
23 R
Line Code Violation Count
Register 1 33 R/W Transmit Channel Blocking Register 2
24 R
Line Code Violation Count
Register 2 34 R/W Transmit Channel Blocking Register 3
25 R
Path Code Violation Count
Register 1 (Note 1) 35 R/W Transmit Control Register 1
26 R
Path Code Violation Count
Register 2 36 R/W Transmit Control Register 2
27 R
Multiframe Out of Sync Count
Register 2 37 R/W Common Control Register 1
28 R Receive FDL Register 38 R/W Common Control Register 2
29 R/W Receive FDL Match Register 1 39 R/W Transmit Transparency Register 1
2A R/W Receive FDL Match Register 2 3A R/W Transmit Transparency Register 2
2B R/W Receive Control Register 1 3B R/W Transmit Transparency Register 3
2C R/W Receive Control Register 2 3C R/W Transmit Idle Register 1
2D R/W Receive Mark Register 1 3D R/W Transmit Idle Register 2
2E R/W Receive Mark Register 2 3E R/W Transmit Idle Register 3
2F R/W Receive Mark Register 3 3F R/W Transmit Idle Definition Register
60 R Receive Signaling Register 1 70 R/W Transmit Signaling Register 1
61 R Receive Signaling Register 2 71 R/W Transmit Signaling Register 2
62 R Receive Signaling Register 3 72 R/W Transmit Signaling Register 3
63 R Receive Signaling Register 4 73 R/W Transmit Signaling Register 4
64 R Receive Signaling Register 5 74 R/W Transmit Signaling Register 5
65 R Receive Signaling Register 6 75 R/W Transmit Signaling Register 6
66 R Receive Signaling Register 7 76 R/W Transmit Signaling Register 7
67 R Receive Signaling Register 8 77 R/W Transmit Signaling Register 8
68 R Receive Signaling Register 9 78 R/W Transmit Signaling Register 9
69 R Receive Signaling Register 10 79 R/W Transmit Signaling Register 10
6A R Receive Signaling Register 11 7A R/W Transmit Signaling Register 11
6B R Receive Signaling Register 12 7B R/W Transmit Signaling Register 12
6C R/W
Receive Channel Blocking
Register 1 7C R/W Line Interface Control Register
6D R/W
Receive Channel Blocking
Register 2 7D R/W Test Register (Note 2)
6E R/W
Receive Channel Blocking
Register 3 7E R/W Transmit FDL Register
6F R/W Interrupt Mask Register 2 7F R/W Interrupt Mask Register 1
Note 1: Address 25 also contains Multiframe Out of Sync Count Register 1.
Note 2: The Test Register is used only by the factory; this register must be cleared (set to all 0s) on power-up initialization to insure proper
operation.
DS2151Q
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3 PARALLEL PORT
The DS2151Q is controlled via a multiplexed bidirectional address/data bus by an external
microcontroller or microprocessor. The DS2151Q can operate with either Intel or Motorola bus timing
configurations. If the BTS pin is tied low, Intel timing will be selected; if tied high, Motorola timing will
be selected. All Motorola bus signals are listed in parentheses (). See the timing diagrams in Section 14
for more details. The multiplexed bus on the DS2151Q saves pins because the address information and
data information share the same signal paths. The addresses are presented to the pins in the first portion of
the bus cycle and data will be transferred on the pins during second portion of the bus cycle. Addresses
must be valid prior to the falling edge of ALE (AS), at which time the DS2151Q latches the address from
the AD0 to AD7 pins. Valid write data must be present and held stable during the later portion of the DS
or WR pulses. In a read cycle, the DS2151Q outputs a byte of data during the latter portion of the DS or
RD pulses. The read cycle is terminated and the bus returns to a high impedance state as RD transitions
high in Intel timing or as DS transitions low in Motorola timing. The DS2151Q can also be easily
connected to nonmultiplexed buses. Refer to the separate application note for a detailed discussion of this
topic.
DS2151Q
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4 CONTROL REGISTERS
The operation of the DS2151Q is configured via a set of eight registers. Typically, the control registers
are only accessed when the system is first powered up. Once the DS2151Q has been initialized, the
control registers will only need to be accessed when there is a change in the system configuration. There
are two Receive Control Registers (RCR1 and RCR2), two Transmit Control Registers (TCR1 and
TCR2), a Line Interface Control Register (LICR), and three Common Control Registers (CCR1, CCR2,
and CCR3). Seven of the eight registers are described below. The LICR is described in Section 13.
RCR1: RECEIVE CONTROL REGISTER 1 (Address = 2B Hex)
(MSB) (LSB)
LCVCRF ARC OOF1 OOF2 SYNCC SYNCT SYNCE RESYNC
SYMBOL POSITION NAME AND DESCRIPTION
LCVCRF RCR1.7
Line Code Violation Count Register Function Select.
0 = do not count excessive 0s
1 = count excessive 0s
ARC RCR1.6
Auto Resync Criteria.
0 = Resync on OOF or RCL event
1 = Resync on OOF only
OOF1 RCR1.5
Out Of Frame Select 1.
0 = 2/4 frame bits in error
1 = 2/5 frame bits in error
OOF2 RCR1.4
Out Of Frame Select 2.
0 = follow RCR1.5
1 = 2/6 frame bits in error
SYNCC RCR1.3
Sync Criteria.
In D4 Framing Mode
0 = search for Ft pattern, then search for Fs pattern
1 = cross couple Ft and Fs pattern
In ESF Framing Mode
0 = search for FPS pattern only
1 = search for FPS and verify with CRC6
SYNCT RCR1.2 Sync Time.
0 = qualify 10 bits
1 = qualify 24 bits
SYNCE RCR1.1 Sync Enable.
0 = auto resync enabled
1 = auto resync disabled
RESYNC RCR1.0 Resync. When toggled from low to high, a resynchronization
of the receive side framer is initiated. Must be cleared and set
again for a subsequent resync.
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RCR2: RECEIVE CONTROL REGISTER 2 (Address = 2C Hex)
(MSB) (LSB)
RCS RZBTSI RSDW RSM RSIO RD4YM FSBE MOSCRF
SYMBOL POSITION NAME AND DESCRIPTION
RCS RCR2.7
Receive Code Select.
0 = idle code (7F Hex)
1 = digital milliwatt code (1E/0B/0B/1E/9E/8B/8B/9E Hex)
RZBTSI RCR2.6
Receive Side ZBTSI Enable.
0 = ZBTSI disabled
1 = ZBTSI enabled
RSDW RCR2.5
RSYNC Double-Wide.
0 = do not pulse double-wide in signaling frames
1 = do pulse double-wide in signaling frames (Note: this bit
must be set to 0 when RCR2.4 = 1 or when RCR2.3 = 1.)
RSM RCR2.4
RSYNC Mode Select.
0 = frame mode (see the timing in Section 14)
1 = multiframe mode (see the timing in Section 14)
RSIO RCR2.3
RSYNC I/O Select.
0 = RSYNC is an output
1 = RSYNC is an input (only valid if elastic store enabled)
(Note: this bit must be set to 0 when CCR1.2 = 0.)
RD4YM RCR2.2
Receive Side D4 Yellow Alarm Select.
0 = 0s in bit 2 of all channels
1 = a 1 in the S-bit position of frame 12
FSBE RCR2.1
PCVCR Fs Bit Error Report Enable.
0 = do not report bit errors in Fs bit position; only Ft bit
position
1 = report bit errors in Fs bit position as well as Ft bit position
MOSCRF RCR2.0
Multiframe Out of Sync Count Register Function Select.
0 = count errors in the framing bit position
1 = count the number of multiframes out of sync
DS2151Q
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TCR1: TRANSMIT CONTROL REGISTER 1 (Address = 35 Hex)
(MSB) (LSB)
LOTCMC TFPT TCPT RBSE GB7S TLINK TBL TYEL
SYMBOL POSITION NAME AND DESCRIPTION
LOTCMC TCR1.7 Loss Of Transmit Clock Mux Control. Determines whether
the transmit side formatter should switch to the ever present
RCLK if the TCLK input should fail to transition (Figure 1-1).
0 = do not switch to RCLK if TCLK stops
1 = switch to RCLK if TCLK stops
TFPT TCR1.6 Transmit Framing Pass Through. (See note below.)
0 = Ft or FPS bits sourced internally
1 = Ft or FPS bits sampled at TSER during F-bit time
TCPT TCR1.5 Transmit CRC Pass Through. (See note below.)
0 = source CRC6 bits internally
1 = CRC6 bits sampled at TSER during F-bit time
RBSE TCR1.4 Robbed-Bit Signaling Enable. (See note below.)
0 = no signaling is inserted in any channel
1 = signaling is inserted in all channels (the TTR registers can
be used to block insertion on a channel by channel basis)
GB7S TCR1.3 Global Bit 7 Stuffing. (See note below.)
0 = allow the TTR registers to determine which channels
containing all 0s are to be Bit 7 stuffed
1 = force Bit 7 stuffing in all 0 byte channels regardless of how
the TTR registers are programmed
TLINK TCR1.2 TLINK Select. (See note below.)
0 = source FDL or Fs bits from TFDL register
1 = source FDL or Fs bits from the TLINK pin
TBL TCR1.1 Transmit Blue Alarm. (See note below.)
0 = transmit data normally
1 = transmit an unframed all 1s code at TPOS and TNEG
TYEL TCR1.0 Transmit Yellow Alarm. (See note below.)
0 = do not transmit yellow alarm
1 = transmit yellow alarm
Note: For a detailed description of how the bits in TCR1 affect the transmit side formatter of the
DS2151Q, see Figure 14-9.
DS2151Q
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TCR2: TRANSMIT CONTROL REGISTER 2 (Address = 36 Hex)
(MSB) (LSB)
TEST1 TEST0 TZBTSI TSDW TSM TSIO TD4YM B7ZS
SYMBOL POSITION NAME AND DESCRIPTION
TEST1 TCR2.7
Test Mode Bit 1 for Output Pins. See Table 4-1.
TEST0 TCR2.6
Test Mode Bit 0 for Output Pins. See Table 4-1.
TZBTSI TCR2.5
Transmit Side ZBTSI Enable.
0 = ZBTSI disabled
1 = ZBTSI enabled
TSDW TCR2.4 TSYNC Double-Wide. (Note: This bit must be set to 0 when
TCR2.3 = 1 or when TCR2.2 = 0.)
0 = do not pulse double-wide in signaling frames
1 = do pulse double-wide in signaling frames
TSM TCR2.3
TSYNC Mode Select.
0 = frame mode (see the timing in Section 14)
1 = multiframe mode (see the timing in Section 14)
TSIO TCR2.2
TSYNC I/O Select.
0 = TSYNC is an input
1 = TSYNC is an output
TD4YM TCR2.1
Transmit Side D4 Yellow Alarm Select.
0 = 0s in bit 2 of all channels
1 = 1 in the S-bit position of frame 12
B7ZS XTCR2.0
Bit 7 Zero Suppression Enable.
0 = No stuffing occurs
1 = Bit 7 force to a 1 in channels with all 0s
Table 4-1. Output Pin Test Modes
TEST1 TEST0 EFFECT ON OUTPUT PINS
0 0 Operate normally
0 1 Force all output pins tri-state (including all I/O pins and parallel port pins)
1 0 Force all output pins low (including all I/O pins except parallel port pins)
1 1 Force all output pins high (including all I/O pins except parallel port pins)
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CCR1: COMMON CONTROL REGISTER 1 (Address = 37 Hex)
(MSB) (LSB)
TESE LLB RSAO RLB SCLKM RESE PLB FLB
SYMBOL POSITION NAME AND DESCRIPTION
TESE CCR1.7
Transmit Elastic Store Enable.
0 = elastic store is bypassed
1 = elastic store is enabled
LLB CCR1.6
Local Loopback.
0 = loopback disabled
1 = loopback enabled
RSAO CCR1.5
Receive Signaling All 1s.
0 = allow robbed signaling bits to appear at RSER
1 = force all robbed signaling bits at RSER to 1
RLB CCR1.4
Remote Loopback.
0 = loopback disabled
1 = loopback enabled
SCLKM CCR1.3
SYSCLK Mode Select.
0 = if SYSCLK is 1.544MHz
1 = if SYSCLK is 2.048MHz
RESE CCR1.2
Receive Elastic Store Enable.
0 = elastic store is bypassed
1 = elastic store is enabled
PLB CCR1.1
Payload Loopback.
0 = loopback disabled
1 = loopback enabled
FLB CCR1.0
Framer Loopback.
0 = loopback disabled
1 = loopback enabled
DS2151Q
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4.1 Local Loopback
When CCR1.6 is set to a 1, the DS2151Q will be forced into Local Loopback (LLB). In this loopback,
data will continue to be transmitted as normal through the transmit side of the SCT. Data being received
at RTIP and RRING will be replaced with the data being transmitted. Data in this loopback will pass
through the jitter attenuator and the jitter attenuator should be programmed to be in the transmit path.
LLB is primarily used in debug and test applications. See Figure 1-1 for more details.
4.2 Remote Loopback
When CCR1.4 is set to a 1, the DS2151Q will be forced into Remote Loopback (RLB). In this loopback,
data recovered off the T1 line from the RTIP and RRING pins will be transmitted back onto the T1 line
(with any BPVs that might have occurred intact) via the TTIP and TRING pins. Data will continue to
pass through the receive side of the DS2151Q as it would normally and the data at the TSER input will be
ignored. Data in this loopback will pass through the jitter attenuator. RLB is used to place the DS2151Q
into “line” loopback, which is a requirement of both ANSI T1.403 and AT&T TR62411. See Figure 1-1
for more details.
4.3 Payload Loopback
When CCR1.1 is set to a 1, the DS2151Q will be forced into Payload Loopback (PLB). Normally, this
loopback is only enabled when ESF framing is being performed. In a PLB situation, the DS2151Q will
loop the 192 bits of payload data (with BPVs corrected) from the receive section back to the transmit
section. The FPS framing pattern, CRC6 calculation, and the FDL bits are not looped back, they are
reinserted by the DS2151Q. When PLB is enabled, the following will occur:
1) Data will be transmitted from the TTIP and TRING pins synchronous with RCLK instead of
TCLK.
2) All the receive side signals will continue to operate normally.
3) The TCHCLK and TCHBLK signals are forced low.
4) Data at the TSER pin is ignored.
5) The TLCLK signal will become synchronous with RCLK instead of TCLK.
4.4 Framer Loopback
When CCR1.0 is set to a 1, the DS2151Q will enter a Framer Loopback (FLB) mode. This loopback is
useful in testing and debugging applications. In FLB, the DS2151Q will loop data from the transmit side
back to the receive side. When FLB is enabled, the following will occur:
1) Unless the RLB is active, an unframed all 1s code will be transmitted at TTIP and TRING.
2) Data off the T1 line at RTIP and RRING will be ignored.
3) The RCLK output will be replaced with the TCLK input.
DS2151Q
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CCR2: COMMON CONTROL REGISTER 2 (Address = 38 Hex)
(MSB) (LSB)
TFM TB8ZS TSLC96 TFDL RFM RB8ZS RSLC96 RFDL
SYMBOL POSITION NAME AND DESCRIPTION
TFM CCR2.7
Transmit Frame Mode Select.
0 = D4 framing mode
1 = ESF framing mode
TB8ZS CCR2.6
Transmit B8ZS Enable.
0 = B8ZS disabled
1 = B8ZS enabled
TSLC96 CCR2.5
Transmit SLC-96/Fs Bit Loading Enable.
0 = SLC-96/Fs bit Loading disabled
1 = SLC-96/Fs bit Loading enabled
TFDL CCR2.4
Transmit FDL 0 Stuffer Enable.
0 = 0 stuffer disabled
1 = 0 stuffer enabled
RFM CCR2.3
Receive Frame Mode Select.
0 = D4 framing mode
1 = ESF framing mode
RB8ZS CCR2.2
Receive B8ZS Enable.
0 = B8ZS disabled
1 = B8ZS enabled
RSLC96 CCR2.1
Receive SLC-96 Enable.
0 = SLC-96 disabled
1 = SLC-96 enabled
RFDL CCR2.0
Receive FDL 0 Destuffer Enable.
0 = 0 destuffer disabled
1 = 0 destuffer enabled
DS2151Q
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CCR3: COMMON CONTROL REGISTER 3 (Address = 30 Hex)
(MSB) (LSB)
ESMDM ESR P16F RSMS PDE TLD TLU LIRST
SYMBOL POSITION NAME AND DESCRIPTION
ESMDM CCR3.7 Elastic Store Minimum Delay Mode. See Section 11 for
details.
0=elastic stores operate at full two-frame depth
1=elastic stores operate at 32-bit depth
ESR CCR3.6 Elastic Store Reset. Setting this bit from a 0 to a 1 will force
the elastic stores to a known depth. Should be toggled after
SYSCLK has been applied and is stable. Must be cleared and
set again for a subsequent reset.
P16F CCR3.5
Function of Pin 16.
0 = Receive Loss of Sync (RLOS).
1 = Loss of Transmit Clock (LOTC).
RSMS CCR3.4 RSYNC Multiframe Skip Control. Useful in framing format
conversions from D4 to ESF.
0 = RSYNC will output a pulse at every multiframe
1 = RSYNC will output a pulse at every other multiframe note:
for this bit to have any affect, the RSYNC must be set to output
multiframe pulses (RCR2.4 = 1 and RCR2.3 = 0) and the
receive elastic store must be bypassed. (CCR1.2 = 0).
PDE CCR3.3
Pulse Density Enforcer Enable.
0 = disable transmit pulse density enforcer
1 = enable transmit pulse density enforcer
TLD CCR3.2
Transmit Loop Down Code (001).
0 = transmit data normally
1 = replace normal transmitted data with Loop Down code
TLU CCR3.1
Transmit Loop Up Code (00001).
0 = transmit data normally
1 = replace normal transmitted data with Loop Up code
LIRST CCR3.0 Line Interface Reset. Setting this bit from a 0 to a one will
initiate an internal reset that affects the slicer, AGC, clock
recovery state machine and jitter attenuator. Normally this bit is
only toggled on power-up. Must be cleared and set again for a
subsequent reset.
DS2151Q
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4.5 Loop Code Generation
When either the CCR3.1 or CCR3.2 bits are set to 1, the DS2151Q will replace the normal transmitted
payload with either the Loop Up or Loop Down code, respectively. The DS2151Q will overwrite the
repeating loop code pattern with the framing bits. The SCT will continue to transmit the loop codes as
long as either bit is set. It is an illegal state to have both CCR3.1 and CCR3.2 set to 1 at the same time.
4.6 Pulse Density Enforcer
The SCT always examines both the transmit and receive data streams for violations of the following rules
which are required by ANSI T1.403-199X:
– no more than 15 consecutive 0s
– at least N 1s in each and every time window of 8 x (N +1) bits where N = 1 through 23
Violations for the transmit and receive data streams are reported in the RIR2.0 and RIR2.1 bits
respectively.
When the CCR3.3 is set to 1, the DS2151Q will force the transmitted stream to meet this requirement no
matter the content of the transmitted stream. When running B8ZS, the CCR3.3 bit should be set to 0,
since B8ZS encoded data streams cannot violate the pulse density requirements.
4.7 Power-Up Sequence
On power-up, after the supplies are stable, the DS2151Q should be configured for operation by writing to
all of the internal registers (this includes setting the Test Register to 00Hex) since the contents of the
internal registers cannot be predicted on power-up. Next, the LIRST bit should be toggled from 0 to 1 to
reset the line interface (it will take the DS2151Q about 40ms to recover from the LIRST being toggled).
Finally, after the SYSCLK input is stable, the ESR bit should be toggled from a 0 to a 1 (this step can be
skipped if the elastic stores are disabled).
DS2151Q
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5 STATUS AND INFORMATION REGISTERS
There is a set of four registers that contain information on the current real time status of the DS2151Q:
Status Register 1 (SR1), Status Register 2 (SR2), Receive Information Register 1 (RIR1), and Receive
Information Register 2 (RIR2). When a particular event has occurred (or is occurring), the appropriate bit
in one of these four registers will be set to a 1. All of the bits in these registers operate in a latched
fashion. This means that if an event occurs and a bit is set to a 1 in any of the registers, it will remain set
until the user reads that bit. The bit will be cleared when it is read and it will not be set again until the
event has occurred again or if the alarm(s) is still present.
The user will always precede a read of these registers with a write. The byte written to the register will
inform the DS2151Q which bits the user wishes to read and have cleared. The user will write a byte to
one of these four registers, with a 1 in the bit positions he or she wishes to read and a 0 in the bit positions
he or she does not wish to obtain the latest information on. When a 1 is written to a bit location, the read
register will be updated with current value and the previous value will be cleared. When a 0 is written to a
bit position, the read register will not be updated and the previous value will be held. A write to the status
and information registers will be immediately followed by a read of the same register. The read result
should be logically ANDed with the mask byte that was just written and this value should be written back
into the same register to ensure that the bit does indeed clear. This second write is necessary because the
alarms and events in the status registers occur asynchronously in respect to their access via the parallel
port. The write-read-write scheme is unique to the four status registers and it allows an external
microcontroller or microprocessor to individually poll certain bits without disturbing the other bits in the
register. This operation is key in controlling the DS2151Q with higher-order software languages.
The SR1 and SR2 registers have the unique ability to initiate a hardware interrupt via the INT1 and INT2
pins, respectively. Each of the alarms and events in the SR1 and SR2 can be either masked or unmasked
from the interrupt pins via the Interrupt Mask Register 1 (IMR1) and Interrupt Mask Register 2 (IMR2)
respectively.
DS2151Q
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RIR1: RECEIVE INFORMATION REGISTER 1 (Address = 22 Hex)
(MSB) (LSB)
COFA 8ZD 16ZD RESF RESE SEFE B8ZS FBE
SYMBOL POSITION NAME AND DESCRIPTION
COFA RIR1.7 Change of Frame Alignment. Set when the last resync
resulted in a change of frame or multiframe alignment.
8ZD RIR1.6 Eight 0 Detect. Set when a string of eight consecutive 0s have
been received at RPOS and RNEG.
16ZD RIR1.5 Sixteen 0 Detect. Set when a string of 16 consecutive 0s have
been received at RPOS and RNEG.
RESF RIR1.4 Receive Elastic Store Full. Set when the receive elastic store
buffer fills and a frame is deleted.
RESE RIR1.3 Receive Elastic Store Empty. Set when the receive elastic
store buffer empties and a frame is repeated.
SEFE RIR1.2 Severely Errored Framing Event. Set when 2 out of 6
framing bits (Ft or FPS) are received in error.
B8ZS RIR1.1 B8ZS Codeword Detect. Set when a B8ZS codeword is
detected at RPOS and RNEG independent of whether the B8ZS
mode is selected or not via CCR2.6.
FBE RIR1.0 Frame Bit Error. Set when a Ft (D4) or FPS (ESF) framing
bit is received in error.
DS2151Q
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RIR2: RECEIVE INFORMATION REGISTER 2 (Address = 31 Hex)
(MSB) (LSB)
RL1 RL0 TESF TESE TSLIP JALT RPDV TPDV
SYMBOL POSITION NAME AND DESCRIPTION
RL1 RIR2.7 Receive Level Bit 1. See Table 5-1.
RL0 RIR2.6 Receive Level Bit 0. See Table 5-1.
TESF RIR2.5 Transmit Elastic Store Full. Set when the transmit elastic
store buffer fills and a frame is deleted.
TESE RIR2.4 Transmit Elastic Store Empty. Set when the transmit elastic
store buffer empties and a frame is repeated.
TSLIP RIR2.3 Transmit Elastic Store Slip Occurrence. Set when the
transmit elastic store has either repeated or deleted a frame.
JALT RIR2.2 Jitter Attenuator Limit Trip. Set when the jitter attenuator
FIFO reaches to within 4 bits of its limit; useful for debugging
jitter attenuation operation.
RPDV RIR2.1 Receive Pulse Density Violation. Set when the receive data
stream does not meet the ANSI T1.403 requirements for pulse
density.
TPDV RIR2.0 Transmit Pulse Density Violation. Set when the transmit data
stream does not meet the ANSI T1.403 requirements for pulse
density.
Table 5-1. Receive T1 Level Indication
RL1 RL0 TYPICAL LEVEL
RECEIVED (dB)
0 0 +2 to -7.5
0 1 -7.5 to -15
1 0 -15 to -22.5
1 1 Less than -22.5
DS2151Q
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SR1: STATUS REGISTER 1 (Address = 20 Hex)
(MSB) (LSB)
LUP LDN LOTC RSLIP RBL RYEL RCL RLOS
SYMBOL POSITION NAME AND DESCRIPTION
LUP SR1.7 Loop Up Code Detected. Set when the repeating ...00001...
loop up code is being received.
LDN SR1.6 Loop Down Code Detected. Set when the repeating ...001...
loop down code is being received.
LOTC SR1.5 Loss of Transmit Clock. Set when the TCLK pin has not
transitioned for one channel time (or 5.2µs). Will force pin 16
high if enabled via CCR1.6. Based on RCLK.
RSLIP SR1.4 Receive Elastic Store Slip Occurrence. Set when the receive
elastic store has either repeated or deleted a frame.
RBL SR1.3 Receive Blue Alarm. Set when a blue alarm is received at
RTIP and RRING. See note below.
RYEL SR1.2 Receive Yellow Alarm. Set when a yellow alarm is received at
RTIP and RRING.
RCL SR1.1 Receive Carrier Loss. Set when 192 consecutive 0s have been
detected at RTIP and RRING.
RLOS SR1.0 Receive Loss of Sync. Set when the device is not synchronized
to the receive T1 stream.
DS2151Q
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Table 5-2. Alarm Set and Clear Criteria
ALARM SET CRITERIA CLEAR CRITERIA
Blue Alarm (AIS) (see note below) When over a 3ms window, five or
less 0s are received
When over a 3ms window, six or
more 0s are received
Yellow Alarm
1. D4 bit 2 mode (RCR2.2=0)
2. D4 12th F-bit mode (RCR2.2=1;
this mode is also referred to as
the “Japanese Yellow Alarm”)
3. ESF Mode
When bit 2 of 256 consecutive
channels is set to 0 for at least 254
occurrences
When the 12th framing bit is set to
1 for two consecutive occurrences
When 16 consecutive patterns of
00FF hex appear in the FDL
When bit 2 of 256 consecutive
channels is set to 0 for less than 254
occurrences
When the 12th framing bit is set to 0
for two consecutive occurrences
When 14 or less patterns of 00FF
hex out of 16 possible appear in the
FDL
Red Alarm (RCL) (this alarm is
also referred to as Loss of Signal)
When 192 consecutive 0s are
received
When 14 or more 1s out of 112
possible bit positions are received
starting with the first 1 received
Note: The definition of Blue Alarm (or Alarm Indication Signal) is an unframed all-ones signal. Blue alarm detectors should
be able to operate properly in the presence of a 10-3 error rate and they should not falsely trigger on a framed all-ones signal.
The blue alarm criteria in the DS2151Q has been set to achieve this performance. It is recommended that the RBL bit be
qualified with the RLOS status bit in detecting a blue alarm.
5.1 Loop Up/Down Code Detection
Bits SR1.7 and SR1.6 will indicate when either the standard Loop Up or Loop Down codes are being
received by the DS2151Q. When a Loop Up code has been received for 5 seconds, the CPE is expected to
loop the recovered data (without correcting BPVs) back to the source. The Loop Down code indicates
that the loopback should be discontinued. See the AT&T publication TR 62411 for more details. The
DS2151Q will detect the Loop Up/Down codes in both framed and unframed circumstances with bit error
rates as high as 10**-2. The loop code detector has a nominal integration period of 48ms. Hence, after
about 48ms of receiving either code, the proper status bit will be set to a 1. After this initial indication, it
is recommended that the software poll the DS2151Q every 100ms to 500ms until 5 seconds have elapsed
to insure that the code is continuously present. Once 5 seconds have passed, the DS2151Q should be
taken into or out of loopback via the Remote Loopback (RLB) bit in CCR1.
DS2151Q
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SR2: STATUS REGISTER 2 (Address = 21 Hex)
(MSB) (LSB)
RMF TMF SEC RFDL TFDL RMTCH RAF -
SYMBOL POSITION NAME AND DESCRIPTION
RMF SR2.7 Receive Multiframe. Set on receive multiframe boundaries.
TMF SR2.6 Transmit Multiframe. Set on transmit multiframe boundaries.
SEC SR2.5 One Second Timer. Set on increments of 1 second based on
RCLK; will be set in increments of 999ms, 999ms, and 1002ms
every 3 seconds.
RFDL SR2.4 Receive FDL Buffer Full. Set when the receive FDL buffer
(RFDL) fills to capacity (8 bits).
TFDL SR2.3 Transmit FDL Buffer Empty. Set when the transmit FDL
buffer (TFDL) empties.
RMTCH SR2.2 Receive FDL Match Occurrence. Set when the RFDL
matches either RFDLM1 or RFDLM2.
RAF SR2.1 Receive FDL Abort. Set when eight consecutive ones are
received in the FDL.
— SR2.0 Not Assigned. Should be set to 0 when written.
DS2151Q
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IMR1: INTERRUPT MASK REGISTER 1 (Address = 7F Hex)
(MSB) (LSB)
LUP LDN LOTC SLIP RBL RYEL RCL RLOS
SYMBOL POSITION NAME AND DESCRIPTION
LUP IMR1.7
Loop Up Code Detected.
0 = interrupt masked
1 = interrupt enabled
LDN IMR1.6
Loop Down Code Detected.
0 = interrupt masked
1 = interrupt enabled
LOTC IMR1.5
Loss of Transmit Clock.
0 = interrupt masked
1 = interrupt enabled
SLIP IMR1.4
Elastic Store Slip Occurrence.
0 = interrupt masked
1 = interrupt enabled
RBL IMR1.3
Receive Blue Alarm.
0 = interrupt masked
1 = interrupt enabled
RYEL IMR1.2
Receive Yellow Alarm.
0 = interrupt masked
1 = interrupt enabled
RCL IMR1.1
Receive Carrier Loss.
0 = interrupt masked
1 = interrupt enabled
RLOS IMR1.0
Receive Loss of Sync.
0 = interrupt masked
1 = interrupt enabled
DS2151Q
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IMR2: INTERRUPT MASK REGISTER 2 (Address = 6F Hex)
(MSB) (LSB)
RMF TMF SEC RFDL TFDL RMTCH RAF —
SYMBOL POSITION NAME AND DESCRIPTION
RMF IMR2.7
Receive Multiframe.
0 = interrupt masked
1 = interrupt enabled
TMF IMR2.6
Transmit Multiframe.
0 = interrupt masked
1 = interrupt enabled
SEC IMR2.5
One-Second Timer.
0 = interrupt masked
1 = interrupt enabled
RFDL IMR2.4
Receive FDL Buffer Full.
0 = interrupt masked
1 = interrupt enabled
TFDL IMR2.3
Transmit FDL Buffer Empty.
0 = interrupt masked
1 = interrupt enabled
RMTCH IMR2.2
Receive FDL Match Occurrence.
0 = interrupt masked
1 = interrupt enabled
RAF IMR2.1
Receive FDL Abort.
0 = interrupt masked
1 = interrupt enabled
— IMR2.0 Not Assigned. Should be set to 0 when written to.
DS2151Q
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6 ERROR COUNT REGISTERS
There are a set of three counters in the DS2151Q that record bipolar violations, excessive 0s, errors in the
CRC6 codewords, framing bit errors, and number of multiframes that the device is out of receive
synchronization. Each of these three counters are automatically updated on one second boundaries as
determined by the one second timer in Status Register 2 (SR2.5). Hence, these registers contain
performance data from the previous second. The user can use the interrupt from the 1-second timer to
determine when to read these registers. The user has a full second to read the counters before the data is
lost. All three counters will saturate at their respective maximum counts and they will not rollover (note:
only the Line Code Violation Count Register has the potential to overflow).
6.1 Line Code Violation Count Register (LCVCR)
Line Code Violation Count Register 1 (LCVCR1) is the most significant word and LCVCR2 is the least
significant word of a 16-bit counter that records code violations (CVs). CVs are defined as Bipolar
Violations (BPVs) or excessive 0s. See Table 6-1 for details of exactly what the LCVCRs count. If the
B8ZS mode is set for the receive side via CCR2.2, then B8ZS codewords are not counted. This counter is
always enabled; it is not disabled during receive loss of synchronization (RLOS = 1) conditions.
LCVCR1: LINE CODE VIOLATION COUNT REGISTER 1 (Address = 23 Hex)
LCVCR2: LINE CODE VIOLATION COUNT REGISTER 2 (Address = 24 Hex)
(MSB) (LSB)
LCV15 LCV14 LCV13 LCV12 LCV11 LCV10 LCV9 LCV8 LCVCR1
LCV7 LCV6 LCV5 LCV4 LCV3 LCV2 LCV1 LCV0 LCVCR2
SYMBOL POSITION NAME AND DESCRIPTION
LCV15 LCVCR1.7 MSB of the 16-bit code violation count
LCV0 LCVCR2.0 LSB of the 16-bit code violation count
Table 6-1. Line Code Violation Counting Arrangements
COUNT
EXCESSIVE 0S?
(RCR1.7)
B8ZS
ENABLED?
(CCR2.2)
WHAT IS COUNTED
IN THE
LCVCRs
No No BPVs
Yes No BPVs + 16 consecutive 0s
No Yes
BPVs (B8ZS codewords
not counted)
Yes Yes BPVs + 8 consecutive 0s
DS2151Q
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6.2 Path Code Violation Count Register (PCVCR)
When the receive side of the DS2151Q is set to operate in the ESF framing mode (CCR2.3 = 1), PCVCR
will automatically be set as a 12-bit counter that will record errors in the CRC6 codewords. When set to
operate in the D4 framing mode (CCR2.3 = 0), PCVCR will automatically count errors in the Ft framing
bit position. Via the RCR2.1 bit, the DS2151Q can be programmed to also report errors in the Fs framing
bit position. The PCVCR will be disabled during receive loss of synchronization (RLOS = 1) conditions.
See Table 6-2 for a detailed description of exactly what errors the PCVCR counts.
PCVCR1: PATH VIOLATION COUNT REGISTER 1 (Address = 25 Hex)
PCVCR2: PATH VIOLATION COUNT REGISTER 2 (Address = 26 Hex)
(MSB) (LSB)
(Note 1) (Note 1) (Note 1) (Note 1) CRC/FB11 CRC/FB10 CRC/FB9 CRC/FB8 PCVCR1
CRC/FB7 CRC/FB6 CRC/FB5 CRC/FB4 CRC/FB3 CRC/FB2 CRC/FB1 CRC/FB0 PCVCR2
SYMBOL POSITION NAME AND DESCRIPTION
CRC/FB11 PCVCR1.3 MSB of the 12-Bit CRC6 Error or Frame Bit Error
Count (Note 2)
CRC/FB0 PCVCR2.0 LSB of the 12-Bit CRC6 Error or Frame Bit Error Count
(Note 2)
Note 1: The upper nibble of the counter at address 25 is used by the Multiframes Out of Sync Count Register.
Note 2: PCVCR counts either errors in CRC codewords (in the ESF framing mode; CCR2.3 = 1) or errors in the framing bit position (in the
D4 framing mode; CCR2.3 = 0).
Table 6-2. Path Code Violation Counting Arrangements
FRAMING MODE
(CCR2.3)
COUNT FS ERRORS?
(RCR2.1)
WHAT IS COUNTED
IN THE PCVCRs
D4 No Errors in the Ft pattern
D4 Yes Errors in both the Ft and Fs patterns
ESF Don’t Care Errors in the CRC6 codewords
DS2151Q
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6.3 Multiframes Out of Sync Count Register (MOSCR)
Normally the MOSCR is used to count the number of multiframes that the receive synchronizer is out of
sync (RCR2.0 = 1). This number is useful in ESF applications needing to measure the parameters Loss Of
Frame Count (LOFC) and ESF Error Events as described in AT&T publication TR54016. When the
MOSCR is operated in this mode, it is not disabled during receive loss of synchronization (RLOS = 1)
conditions. The MOSCR has alternate operating mode whereby it will count either errors in the Ft
framing pattern (in the D4 mode) or errors in the FPS framing pattern (in the ESF mode). When the
MOSCR is operated in this mode, it is disabled during receive loss of synchronization (RLOS = 1)
conditions. See Table 6-3 for a detailed description of what the MOSCR is capable of counting.
MOSCR1: MULTIFRAMES OUT OF SYNC COUNT REGISTER 1 (Address = 25
Hex)
MOSCR2: MULTIFRAMES OUT OF SYNC COUNT REGISTER 2 (Address = 27
Hex)
(MSB) (LSB)
MOS/FB11 MOS/FB10 MOS/FB9 MOS/FB8 (Note 1) (Note 1) (Note 1) (Note 1) MOSCR1
MOS/FB7 MOS/FB6 MOS/FB5 MOS/FB4 MOS/FB3 MOS/FB2 MOS/FB1 MOS/FB0 MOSCR2
SYMBOL POSITION NAME AND DESCRIPTION
MOS/FB11 MOSCR1.7 MSB of the 12-Bit Multiframes Out of Sync or F-Bit
Error Count (Note 2)
MOS/FB0 MOSCR2.0 LSB of the 12-Bit Multiframes Out of Sync or F-Bit Error
Count (Note 2)
Note 1: The lower nibble of the counter at address 25 is used by the Path Code Violation Count Register.
Note 2: MOSCR counts either errors in framing bit position (RCR2.0 = 0) or the number of multiframes out of sync (RCR2.0 = 1).
Table 6-3. Multiframes Out of Sync Counting Arrangements
FRAMING MODE
(CCR2.3)
COUNT MOS OR F-BIT
ERRORS? (RCR2.0)
WHAT IS COUNTED
IN THE MOSCRs
D4 MOS Number of multiframes out of sync
D4 F-Bit Errors in the Ft pattern
ESF MOS Number of multiframes out of sync
ESF F-Bit Errors in the FPS pattern
DS2151Q
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7 FDL/FS EXTRACTION AND INSERTION
The DS2151Q can extract/insert data from/into the Facility Data Link (FDL) in the ESF framing mode
and from/into Fs bit position in the D4 framing mode. Since SLC-96 utilizes the Fs bit position, this
capability can also be used in SLC-96 applications. The operation of the receive and transmit sections
will be discussed separately.
7.1 Receive Section
In the receive section, the recovered FDL bits or Fs bits are shifted bit-by-bit into the Receive FDL
register (RFDL). Since the RFDL is 8 bits in length, it will fill up every 2ms (8 times 250µs). The
DS2151Q will signal an external microcontroller that the buffer has filled via the SR2.4 bit. If enabled via
IMR2.4, the INT2 pin will toggle low indicating that the buffer has filled and needs to be read. The user
has 2ms to read this data before it is lost. If the byte in the RFDL matches either of the bytes programmed
into the RFDLM1 or RFDLM2 registers, then the SR2.2 bit will be set to a 1 and the INT2 pin will be
toggled low if enabled via IMR2.2. This feature allows an external microcontroller to ignore the FDL or
Fs pattern until an important event occurs.
The DS2151Q also contains a 0 destuffer that is controlled via the CCR2.0 bit. In both ANSI T1.403 and
TR54016, communications on the FDL follows a subset of a LAPD protocol. The LAPD protocol states
that no more than five 1s should be transmitted in a row so that the data does not resemble an opening or
closing flag (01111110) or an abort signal (11111111). If enabled via CCR2.0, the DS2151Q will
automatically look for five 1s in a row, followed by a 0. If it finds such a pattern, it will automatically
remove the 0. If the 0 destuffer sees six or more 1s in a row followed by a 0, the 0 is not removed. The
CCR2.0 bit should always be set to a 1 when the DS2151Q is extracting the FDL. More on how to use the
DS2151Q in FDL and SLC-96 applications is covered in a separate application note. Also, contact the
factory for C code software that implements both ANSI T1.403 and AT&T TR54016.
RFDL: RECEIVE FDL REGISTER (Address = 28 Hex)
(MSB) (LSB)
RFDL7 RFDL6 RFDL5 RFDL4 RFDL3 RFDL2 RFDL1 RFDL0
SYMBOL POSITION NAME AND DESCRIPTION
RFDL7 RFDL.7 MSB of the Received FDL Code
RFDL0 RFDL.0 LSB of the Received FDL Code
The Receive FDL Register (RFDL) reports the incoming Facility Data Link (FDL) or the incoming Fs
bits. The LSB is received first.
DS2151Q
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RFDLM1: RECEIVE FDL MATCH REGISTER 1 (Address = 29 Hex)
RFDLM2: RECEIVE FDL MATCH REGISTER 2 (Address = 2A Hex)
(MSB) (LSB)
RFDL7 RFDL6 RFDL5 RFDL4 RFDL3 RFDL2 RFDL1 RFDL0
SYMBOL POSITION NAME AND DESCRIPTION
RFDL7 RFDL.7 MSB of the FDL Match Code
RFDL0 RFDL.0 LSB of the FDL Match Code
When the byte in the Receive FDL Register matches either of the two Receive FDL Match Registers
(RFDLM1/RFDLM2), SR2.2 will be set to a 1 and the INT2 will go active if enabled via IMR2.2.
7.2 Transmit Section
The transmit section will shift out into the T1 data stream, either the FDL (in the ESF framing mode) or
the Fs bits (in the D4 framing mode) contained in the Transmit FDL register (TFDL). When a new value
is written to the TFDL, it will be multiplexed serially (LSB first) into the proper position in the outgoing
T1 data stream. After the full 8 bits have been shifted out, the DS2151Q will signal the host
microcontroller that the buffer is empty and that more data is needed by setting the SR2.3 bit to a 1. The
INT2 will also toggle low if enabled via IMR2.3. The user has 2ms to update the TFDL with a new value.
If the TFDL is not updated, the old value in the TFDL will be transmitted once again.
The DS2151Q also contains a 0 stuffer that is controlled via the CCR2.4 bit. In both ANSI T1.403 and
TR54016, communications on the FDL follows a subset of a LAPD protocol. The LAPD protocol states
that no more than five 1s should be transmitted in a row so that the data does not resemble an opening or
closing flag (01111110) or an abort signal (11111111). If enabled via CCR2.4, the DS2151Q will
automatically look for five 1s in a row. If it finds such a pattern, it will automatically insert a 0 after the
five 1s. The CCR2.4 bit should always be set to a 1 when the DS2151Q is inserting the FDL. More on
how to use the DS2151Q in FDL and SLC-96 applications is covered in a separate application note.
TFDL: TRANSMIT FDL REGISTER (Address = 7E Hex)
(MSB) (LSB)
TFDL7 TFDL6 TFDL5 TFDL4 TFDL3 TFDL2 TFDL1 TFDL0
SYMBOL POSITION NAME AND DESCRIPTION
TFDL7 TFDL.7 MSB of the FDL code to be transmitted
TFDL0 TFDL.0 LSB of the FDL code to be transmitted
The Transmit FDL Register (TFDL) contains the Facility Data Link (FDL) information that is to be
inserted on a byte basis into the outgoing T1 data stream in ESF mode. The LSB is transmitted first. In
D4 operation the TFDL can be the source of the Fs pattern. In this case a 1ch is written to the TFDL
register.
DS2151Q
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8 SIGNALING OPERATION
The Robbed-Bit signaling bits embedded in the T1 stream can be extracted from the receive stream and
inserted into the transmit stream by the DS2151Q. There is a set of 12 registers for the receive side (RS1
to RS12) and 12 registers on the transmit side (TS1 to TS12). The signaling registers are detailed below.
The CCR1.5 bit is used to control the robbed signaling bits as they appear at RSER. If CCR1.5 is set to 0,
then the robbed signaling bits will appear at RSER in their proper position as they are received. If
CCR1.5 is set to a 1, then the robbed signaling bit positions will be forced to a 1 at RSER.
RS1 TO RS12: RECEIVE SIGNALING REGISTERS (Address = 60 to 6B Hex)
(MSB) (LSB)
A(8) A(7) A(6) A(5) A(4) A(3) A(2) A(1) RS1 (60)
A(16) A(15) A(14) A(13) A(12) A(11) A(10) A(9) RS2 (61)
A(24) A(23) A(22) A(21) A(20) A(19) A(18) A(17) RS3 (62)
B(8) B(7) B(6) B(5) B(4) B(3) B(2) B(1) RS4 (63)
B(16) B(15) B(14) B(13) B(12) B(11) B(10) B(9) RS5 (64)
B(24) B(23) B(22) B(21) B(20) B(19) B(18) B(17) RS6 (65)
A/C(8) A/C(7) A/C(6) A/C(5) A/C(4) A/C(3) A/C(2) A/C(1) RS7 (66)
A/C(16) A/C(15) A/C(14) A/C(13) A/C(12) A/C(11) A/C(10) A/C(9) RS8 (67)
A/C(24) A/C(23) A/C(22) A/C(1) A/C(20) A/C(19) A/C(18) A/C(17) RS9 (68)
B/D(8) B/D(7) B/D(6) B/D(5) B/D(4) B/D(3) B/D(2) B/D(1) RS10 (69)
B/D(16) B/D(15) B/D(14) B/D(13) B/D(12) B/D(11) B/D(10) B/D(9) RS11 (6A)
B/D(24) B/D(23) B/D(22) B/D(21) B/D(20) B/D(19) B/D(18) B/D(17) RS12 (6B)
SYMBOL POSITION NAME AND DESCRIPTION
D(24) RS12.7 Signaling Bit D in Channel 24
A(1) RS1.0 Signaling Bit A in Channel 1
Each Receive Signaling Register (RS1 to RS12) reports the incoming Robbed-Bit signaling from eight
DS0 channels. In the ESF framing mode, there can be up to 4 signaling bits per channel (A, B, C, and D).
In the D4 framing mode, there are only 2 framing bits per channel (A and B). In the D4 framing mode,
the DS2151Q will replace the C and D signaling bit positions with the A and B signaling bits from the
previous multiframe. Hence, whether the DS2151Q is operated in either framing mode, the user needs
only to retrieve the signaling bits every 3ms. The bits in the Receive Signaling Registers are updated on
multiframe boundaries so the user can utilize the Receive Multiframe Interrupt in the Receive Status
Register 2 (SR2.7) to know when to retrieve the signaling bits. The Receive Signaling Registers are
frozen and not updated during a loss of sync condition (SR1.0 = 1). They will contain the most recent
signaling information before the “OOF” occurred.
DS2151Q
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TS1 TO TS12: TRANSMIT SIGNALING REGISTERS (Address = 70 to 7B Hex)
(MSB) (LSB)
A(8) A(7) A(6) A(5) A(4) A(3) A(2) A(1) TS1 (70)
A(16) A(15) A(14) A(13) A(12) A(11) A(10) A(9) TS2 (71)
A(24) A(23) A(22) A(21) A(20) A(19) A(18) A(17) TS3 (72)
B(8) B(7) B(6) B(5) B(4) B(3) B(2) B(1) TS4 (73)
B(16) B(15) B(14) B(13) B(12) B(11) B(10) B(9) TS5 (74)
B(24) B(23) B(22) B(21) B(20) B(19) B(18) B(17) TS6 (75)
A/C(8) A/C(7) A/C(6) A/C(5) A/C(4) A/C(3) A/C(2) A/C(1) TS7 (76)
A/C(16) A/C(15) A/C(14) A/C(13) A/C(12) A/C(11) A/C(10) A/C(9) TS8 (77)
A/C(24) A/C(23) A/C(22) A/C(1) A/C(20) A/C(19) A/C(18) A/C(17) TS9 (78)
B/D(8) B/D(7) B/D(6) B/D(5) B/D(4) B/D(3) B/D(2) B/D(1) TS10 (79)
B/D(16) B/D(15) B/D(14) B/D(13) B/D(12) B/D(11) B/D(10) B/D(9) TS11 (7A)
B/D(24) B/D(23) B/D(22) B/D(21) B/D(20) B/D(19) B/D(18) B/D(17) TS12 (7B)
SYMBOL POSITION NAME AND DESCRIPTION
D(24) TS12.7 Signaling Bit D in Channel 24
A(1) TS1.0 Signaling Bit A in Channel 1
Each Transmit Signaling Register (TS1 to TS12) contains the Robbed-Bit signaling for eight DS0
channels that will be inserted into the outgoing stream if enabled to do so via TCR1.4. In the ESF framing
mode, there can be up to 4 signaling bits per channel (A, B, C, and D). On multiframe boundaries, the
DS2151Q will load the values present in the Transmit Signaling Register into an outgoing signaling shift
register that is internal to the device. The user can utilize the Transmit Multiframe Interrupt in Status
Register 2 (SR2.6) to know when to update the signaling bits. In the ESF framing mode, the interrupt will
come every 3ms and the user has a full 3ms to update the TSRs. In the D4 framing mode, there are only 2
framing bits per channel (A and B). However in the D4 framing mode, the DS2151Q uses the C and D bit
positions as the A and B bit positions for the next multiframe. The DS2151Q will load the values in the
TSRs into the outgoing shift register every other D4 multiframe.
DS2151Q
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9 TRANSMIT TRANSPARENCY AND IDLE REGISTERS
There is a set of seven registers in the DS2151Q that can be used to custom tailor the data that is to be
transmitted onto the T1 line, on a channel-by-channel basis. Each of the 24 T1 channels can be either
forced to be transparent or to have a user defined idle code inserted into them. Each of these special
registers is defined below.
TTR1/TTR2/TTR3: TRANSMIT TRANSPARENCY REGISTERS (Address = 39
to 3B Hex)
(MSB) (LSB)
CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 TTR1 (39)
CH16 CH15 CH14 CH13 CH12 CH11 CH10 CH9 TTR2 (3A)
CH24 CH23 CH22 CH21 CH20 CH19 CH18 CH17 TTR3 (3B)
SYMBOL POSITION NAME AND DESCRIPTION
CH24 TTR3.7
Transmit Transparency Registers.
0 = this DS0 channel is not transparent
CH1 TTR1.0 1 = this DS0 channel is transparent
Each of the bit positions in the Transmit Transparency Registers (TTR1/TTR2/TTR3) represents a DS0
channel in the outgoing frame. When these bits are set to a 1, the corresponding channel is transparent (or
clear). If a DS0 is programmed to be clear, no Robbed-Bit signaling will be inserted nor will the channel
have Bit 7 stuffing performed. However, in the D4 framing mode, Bit 2 will be overwritten by a 0 when a
Yellow Alarm is transmitted. Also the user has the option to prevent the TTR registers from determining
which channels are to have Bit 7 stuffing performed. If the TCR2.0 and TCR1.3 bits are set to 1, then all
24 T1 channels will have Bit 7 stuffing performed on them regardless of how the TTR registers are
programmed. In this manner, the TTR registers are only affecting which channels are to have Robbed-Bit
signaling inserted into them. See Figure 14-9 for more details.
TIR1/TIR2/TIR3: TRANSMIT IDLE REGISTERS (Address = 3C to 3E Hex)
(MSB) (LSB)
CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 TIR1 (3C)
CH16 CH15 CH14 CH13 CH12 CH11 CH10 CH9 TIR2 (3D)
CH24 CH23 CH22 CH21 CH20 CH19 CH18 CH17 TIR3 (3E)
SYMBOL POSITION NAME AND DESCRIPTION
CH24 TIR3.7
Transmit Idle Registers.
0 = do not insert the Idle Code into this DS0 channel
CH1 TIR1.0 1 = insert the Idle Code into this channel
DS2151Q
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TIDR: TRANSMIT IDLE DEFINITION REGISTER (Address = 3F Hex)
(MSB) (LSB)
TIDR7 TIDR6 TIDR5 TIDR4 TIDR3 TIDR2 TIDR1 TIDR0
SYMBOL POSITION NAME AND DESCRIPTION
TIDR7 TIDR.7
MSB of the Idle Code
TIDR0 TIDR.0
LSB of the Idle Code
Each of the bit positions in the Transmit Idle Registers (TIR1/TIR2/TIR3) represents a DS0 channel in
the outgoing frame. When these bits are set to a 1, the corresponding channel will transmit the Idle Code
contained in the Transmit Idle Definition Register (TIDR). Robbed-Bit signaling and Bit 7 stuffing will
occur over the programmed Idle Code unless the DS0 channel is made transparent by the Transmit
Transparency Registers.
DS2151Q
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10 CLOCK BLOCKING REGISTERS
The Receive Channel Blocking Registers (RCBR1/RCBR2/RCBR3) and the Transmit Channel Blocking
Registers (TCBR1/TCBR2/TCBR3) control the RCHBLK and TCHBLK pins, respectively. The
RCHBLK and TCHCLK pins are user-programmable outputs that can be forced either high or low during
individual channels. These outputs can be used to block clocks to a USART or LAPD controller in
Fractional T1 or ISDN-PRI applications. When the appropriate bits are set to a 1, the RCHBLK and
TCHCLK pins will be held high during the entire corresponding channel time. See the timing diagrams in
Section 14 for an example.
RCBR1/RCBR2/RCBR3: RECEIVE CHANNEL BLOCKING REGISTERS
(Address = 6C to 6E Hex)
(MSB) (LSB)
CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 RCBR1 (6C)
CH16 CH15 CH14 CH13 CH12 CH11 CH10 CH9 RCBR2 (6D)
CH24 CH23 CH22 CH21 CH20 CH19 CH18 CH17 RCBR3 (6E)
SYMBOL POSITION NAME AND DESCRIPTION
CH24 RCBR3.7
Receive Channel Blocking Registers
0 = force the RCHBLK pin to remain low during this
channel time
CH1 RCBR1.0 1 = force the RCHBLK pin high during this channel time
TCBR1/TCBR2/TCBR3: TRANSMIT CHANNEL BLOCKING REGISTERS
(Address = 32 to 34 Hex)
(MSB) (LSB)
CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 TCBR1 (32)
CH16 CH15 CH14 CH13 CH12 CH11 CH10 CH9 TCBR2 (33)
CH24 CH23 CH22 CH21 CH20 CH19 CH18 CH17 TCBR3 (34)
SYMBOL POSITION NAME AND DESCRIPTION
CH24 TCBR3.7
Transmit Channel Blocking Registers.
0 = force the TCHBLK pin to remain low during this
channel time
CH1 TCBR1.0 1 = force the TCHBLK pin high during this channel time
DS2151Q
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11 ELASTIC STORES OPERATION
The DS2151Q has two on-board two-frame (386 bits) elastic stores. These elastic stores have two main
purposes. First, they can be used to rate-convert the T1 data stream to 2.048Mbps (or a multiple of
2.048Mbps), which is the E1 rate. Secondly, they can be used to absorb the differences in frequency and
phase between the T1 data stream and an asynchronous (i.e., not frequency locked) backplane clock. Both
elastic stores contain full controlled slip capability, which is necessary for this second purpose. The
receive side elastic store can be enabled via CCR1.2 and the transmit side elastic store is enabled via
CCR1.7. The elastic stores can be forced to a known depth via the Elastic Store Reset bit (CCR3.6).
11.1 Receive Side
If the receive side elastic store is enabled (CCR1.2 = 1), then the user must provide either a 1.544MHz
(CCR1.3 = 0) or 2.048MHz (CCR1.3 = 1) clock at the SYSCLK pin. The user has the option of either
providing a frame sync at the RSYNC pin (RCR2.3 = 1) or having the RSYNC pin provide a pulse on
frame boundaries (RCR2.3 = 0). If the user wishes to obtain pulses at the frame boundary, then RCR2.4
must be set to 0 and if the user wishes to have pulses occur at the multiframe boundary, then RCR2.4
must be set to 1. If the user selects to apply a 2.048 MHz clock to the SYSCLK pin, then the data output
at RSER will be forced to all 1s every fourth channel and the F-bit will be deleted. Hence, channels 1, 5,
9, 13, 17, 21, 25, and 29 (time slots 0, 4, 8, 12, 16, 20, 24, and 28) will be forced to a 1.
Also, in 2.048MHz applications, the RCHBLK output will be forced high during the same channels as the
RSER pin. See Section 16 for more details. This is useful in T1 to CEPT (E1) conversion applications. If
the 386-bit elastic buffer either fills or empties, a controlled slip will occur. If the buffer empties, then a
full frame of data (193 bits) will be repeated at RSER and the SR1.4 and RIR1.3 bits will be set to a 1. If
the buffer fills, then a full frame of data will be deleted and the SR1.4 and RIR1.4 bits will be set to a 1.
11.2 Transmit Side
The transmit side elastic store can only be used if the receive side elastic store is enabled. The operation
of the transmit elastic store is very similar to the receive side; both have controlled slip operation and both
can operate with either a 1.544MHz or a 2.048MHz SYSCLK. When the transmit elastic store is enabled,
both the SYSCLK and RSYNC signals are shared by both the elastic stores. Hence, they will have the
same backplane PCM frame and data structure. Controlled slips in the transmit elastic store are reported
in the RIR2.5 bit and the direction of the slip is reported in the RIR2.3 and RIR2.4 bits.
11.3 Minimum Delay Synchronous SYSCLK Mode
In applications where the DS2151Q is connected to backplanes that are frequency-locked to the recovered
T1 clock (i.e., the RCLK output), the full two-frame depth of the onboard elastic stores is really not
needed. In fact, in some delay-sensitive applications the normal two-frame depth may be excessive. If the
CCR3.7 bit is set to 1, then the receive elastic store (and also the transmit elastic store if it is enabled) will
be forced to a maximum depth of 32 bits instead of the normal 386 bits. In this mode, the SYSCLK must
be frequency-locked to RCLK and all of the slip contention logic in the DS2151Q is disabled (since slips
cannot occur). Also, since the buffer depth is no longer two frames deep, the DS2151Q must be set up to
source either a frame or multiframe pulse at the RSYNC pin. On power-up after the SYSCLK has locked
to the RCLK signal, the Elastic Store Reset bit (CCR3.6) should be toggled from a 0 to a 1 to ensure
proper operation.
DS2151Q
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12 RECEIVE MARK REGISTERS
The DS2151Q can replace the incoming data on a channel-by-channel basis with either an idle code (7F
hex) or the digital milliwatt code, which is an 8-byte repeating pattern that represents a 1kHz sine wave
(1E/0B/0B/1E/9E/8B/8B/9E). The RCR2.7 bit will determine which code is used. Each bit in the RMRs,
represents a particular channel. If a bit is set to a 1, then the receive data in that channel will be replaced
with one of the two codes. If a bit is set to 0, no replacement occurs.
RMR1/RMR2/RMR3: RECEIVE MARK REGISTERS (Address=2D to 2F Hex)
(MSB) (LSB)
CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 RMR1 (2D)
CH16 CH15 CH14 CH13 CH12 CH11 CH10 CH9 RMR2 (2E)
CH24 CH23 CH22 CH21 CH20 CH19 CH18 CH17 RMR3 (2F)
SYMBOL POSITION NAME AND DESCRIPTION
CH24 RMR3.7 Receive Channel Blocking Registers.
0 = do not affect the receive data associated with this
channel
CH1 RMR1.0 1 = replace the receive data associated with this channel
with either the idle code or the digital milliwatt code
(depends on the RCR2.7 bit)
DS2151Q
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13 LINE INTERFACE FUNCTIONS
The line interface function in the DS2151Q contains three sections: the receiver, which handles clock and
data recovery; the transmitter, which waveshapes and drives the T1 line; and the jitter attenuator. Each of
these three sections is controlled by the Line Interface Control Register (LICR), which is described
below.
LICR: LINE INTERFACE CONTROL REGISTER (Address = 7C Hex)
(MSB) (LSB)
LB2 LB1 LB0 EGL JAS JABDS DJA TPD LICR
SYMBOL POSITION NAME AND DESCRIPTION
LB2 LICR.7 Line Build-Out Select Bit 2. Sets the transmitter build
out; see the Table 13-2.
LB1 LICR.6 Line Build-Out Select Bit 1. Sets the transmitter build
out; see the Table 13-2.
LB0 LICR.5 Line Build-Out Select Bit 0. Sets the transmitter build
out; see the Table 13-2.
EGL LICR.4 Receive Equalizer Gain Limit.
0 = -36dB
1 = -30dB
JAS LICR.3 Jitter Attenuator Select.
0 = place the jitter attenuator on the receive side
1 = place the jitter attenuator on the transmit side
JABDS LICR.2 Jitter Attenuator Buffer Depth Select.
0 = 128 bits
1 = 32 bits (use for delay sensitive applications)
DJA LICR.1 Disable Jitter Attenuator.
0 = jitter attenuator enabled
1 = jitter attenuator disabled
TPD LICR.0 Transmit Power Down.
0 = normal transmitter operation
1 = powers down the transmitter and tri-states the TTIP
and TRING pins
DS2151Q
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13.1 Receive Clock and Data Recovery
The DS2151Q contains a digital clock recovery system. See Figure 1-1 and Figure 13-1 for more details.
The DS2151Q couples to the receive T1 twisted pair via a 1:1 transformer. See Table 13-3 for
transformer details. The DS2151Q automatically adjusts to the T1 signal being received at the RTIP and
RRING pins and can handle T1 lines from 0 feet to over 6000 feet in length. The crystal attached at the
XTAL1 and XTAL2 pins is multiplied by 4 via an internal PLL and fed to the clock recovery system. The
clock recovery system uses both edges of the clock from the PLL circuit to form a 32 times oversampler
which is used to recover the clock and data. This oversampling technique offers outstanding jitter
tolerance (see Figure 13-2). The EGL bit in the Line Interface Control Register is used to limit the
sensitivity of the receiver in the DS2151Q. For most CPE applications, a receiver sensitivity of -30dB is
wholly sufficient and hence the EGL bit should be set to 1. In some applications, more sensitivity than
-30dB may be required and the DS2151Q will allow the receiver to go as low as -36dB if the EGL bit is
set to 0. However, when the EGL bit is set to 0, the DS2151Q will be more susceptible to crosstalk and its
jitter tolerance will suffer.
Normally, the clock that is output at the RCLK pin is the recovered clock from the T1 AMI waveform
presented at the RTIP and RRING inputs. When no AMI signal is present at RTIP and RRING, a Receive
Carrier Loss (RCL) condition will occur and the RCLK can be sourced from either the ACLKI pin or
from the crystal attached to the XTAL1 and XTAL2 pins. The DS2151Q will sense the ACLKI pin to
determine if a clock is present. If no clock is applied to the ACLKI pin, then it should be tied to RVSS to
prevent the device from falsely sensing a clock. See Table 13-1. If the jitter attenuator is either placed in
the transmit path or is disabled, the RCLK output can exhibit short high cycles of the clock. This is due to
the highly oversampled digital clock recovery circuitry. If the jitter attenuator is placed in the receive path
(as is the case in most applications), the jitter attenuator restores the RCLK to being close to 50% duty
cycle. See the receive AC timing characteristics in Section 16 for more details.
Table 13-1. Source of RCLK Upon RCL
ACLKI PRESENT? RECEIVE SIDE JITTER
ATTENUATOR
TRANSMIT SIDE JITTER
ATTENUATOR
Yes ACLKI via the jitter attenuator ACLKI
No Centered crystal TCLK via the jitter attenuator
DS2151Q
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13.2 Transmit Waveshaping and Line Driving
The DS2151Q uses a set of laser-trimmed delay lines along with a precision Digital-to-Analog Converter
(DAC) to create the waveforms that are transmitted onto the T1 line. The waveforms created by the
DS2151Q meet the latest ANSI, AT&T, and CCITT specifications. See Figure 13-3. The user will select
which waveform is to be generated by properly programming the L0 to L2 bits in the Line Interface
Control Register (LICR).
Table 13-2. LBO Select in LICR
L2 L1 L0 LINE BUILD-OUT APPLICATION
0 0 0 0 to 133 feet/0dB DSX-1/CSU
0 0 1 133 to 266 feet DSX-1
0 1 0 266 to 399 feet DSX-1
0 1 1 399 to 533 feet DSX-1
1 0 0 533 to 655 feet DSX-1
1 0 1 -7.5dB CSU
1 1 0 -15dB CSU
1 1 1 -22.5dB CSU
Due to the nature of the design of the transmitter in the DS2151Q, very little jitter (less than 0.005UIP-P
broadband from 10Hz to 100kHz) is added to the jitter present on TCLK. Also, the waveforms that they
create are independent of the duty cycle of TCLK. The transmitter in the DS2151Q couples to the T1
transmit twisted pair via a 1:1.15 or 1:1.36 step-up transformer as shown in Figure 13-1. For the devices
to create the proper waveforms, the transformer used must meet the specifications listed in Table 13-3.
Table 13-3. Transformer Specifications
SPECIFICATION RECOMMENDED VALUE
Turns Ratio 1:1 (receive) and 1:1.15 or 1:1.36 (transmit) ±5%
Primary Inductance 600µH minimum
Leakage Inductance 1.0µH maximum
Intertwining Capacitance 40pF maximum
DC Resistance 1.2Ω maximum
DS2151Q
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13.3 Jitter Attenuator
The DS2151Q contains an on-board jitter attenuator that can be set to a depth of either 32 or 128 bits via
the JABDS bit in the Line Interface Control Register (LICR). The 128-bit mode is used in applications
where large excursions of wander are expected. The 32-bit mode is used in delay sensitive applications.
The characteristics of the attenuation are shown in Figure 13-4. The jitter attenuator can be placed in
either the receive path or the transmit path by appropriately setting or clearing the JAS bit in the LICR.
Also, the jitter attenuator can be disabled (in effect, removed) by setting the DJA-bit in the LICR. In order
for the jitter attenuator to operate properly, a crystal with the specifications listed in Table 13-4 below
must be connected to the XTAL1 and XTAL2 pins. The jitter attenuator divides the clock provided by the
6.176MHz crystal at the XTAL1 and XTAL2 pins to create an output clock that contains very little jitter.
On-board circuitry will pull the crystal (by switching in or out load capacitance) to keep it long-term
averaged to the same frequency as the incoming T1 signal. If the incoming jitter exceeds either 120UIP-P
(buffer depth is 128 bits) or 28UIP-P (buffer depth is 32 bits), then the DS2151Q will divide the attached
crystal by either 3.5 or 4.5 instead of the normal 4 to keep the buffer from overflowing. When the device
divides by either 3.5 or 4.5, it also sets the Jitter Attenuator Limit Trip (JALT) bit in the Receive
Information Register 2 (RIR2.2).
Table 13-4. Crystal Selection Guidelines
PARAMETER SPECIFICATION
Parallel Resonant Frequency 6.176MHz
Mode Fundamental
Load Capacitance 18pF to 20pF (18.5pF nominal)
Tolerance ±50ppm
Pullability CL = 10pF, delta frequency = +175ppm to
+250ppm
CL = 45pF, delta frequency = -175ppm to -250ppm
Effective Series Resistance 40Ω maximum
Crystal Cut AT
DS2151Q
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Figure 13-1. External Analog Connections
Figure 13-2. Jitter Tolerance
NOTE: SEE THE SEPARATE APPLICATION NOTE FOR DETAILS ON HOW TO CONSTRUCT A PROTECTED INTERFACE.
DS2151Q
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Figure 13-3. Transmit Waveform Template
DS2151Q
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Figure 13-4. Jitter Attenuation
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14 TIMING DIAGRAMS
Figure 14-1. Receive Side D4 Timing
Figure 14-2. Receive Side ESF Timing
NOTE 1: RSYNC IN THE FRAME MODE (RCR2.4 = 0) AND DOUBLE-WIDE FRAME SYNC IS NOT ENABLED (RCR2.5 = 0).
NOTE 2: RSYNC IN THE FRAME MODE (RCR2.4 = 0) AND DOUBLE-WIDE FRAME SYNC IS ENABLED (RCR2.5 = 1).
NOTE 3: RSYNC IN THE MULTIFRAME MODE (RCR2.4 = 1).
NOTE 4: RLINK DATA (S-BIT) IS UPDATED 1 BIT PRIOR TO EVEN FRAMES AND HELD FOR TWO FRAMES.
NOTE 1: RSYNC IN THE FRAME MODE (RCR2.4 = 0) AND DOUBLE-WIDE FRAME SYNC IS NOT ENABLED (RCR2.5 = 0).
NOTE 2: RSYNC IN THE FRAME MODE (RCR2.4 = 0) AND DOUBLE-WIDE FRAME SYNC IS ENABLED (RCR2.5 = 1).
NOTE 3: RSYNC IN THE MULTIFRAME MODE (RCR2.4 = 1).
NOTE 4: ZBTSI MODE DISABLED (RCR2.6 = 0).
NOTE 5: RLINK DATA (FDL BITS) IS UPDATED 1 BIT-TIME BEFORE ODD FRAMES AND HELD FOR TWO FRAMES.
NOTE 6: ZBTSI MODE IS ENABLED (RCR2.6 = 1).
NOTE 7: RLINK DATA (Z BITS) IS UPDATED 1 BIT-TIME BEFORE ODD FRAME AND HELD FOR FOUR FRAMES.
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Figure 14-3. Receive Side Boundary Timing with Elastic Store(s) Disabled
Figure 14-4. 1.544MHz Boundary Timing with Elastic Store(s) Enabled
NOTE 1: RCHBLK IS PROGRAMMED TO BLOCK CHANNEL 24.
NOTE 2: AN ESF BOUNDARY IS SHOWN.
NOTE 1: RSYNC IS IN THE OUTPUT MODE (RCR2.3 = 0).
NOTE 2: RSYNC IS IN THE INPUT MODE (RCR2.3 = 1).
NOTE 3: RCHBLK IS PROGRAMMED TO BLOCK CHANNEL 24.
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Figure 14-5. 2.048MHz Boundary Timing with Elastic Store(s) Enabled
Figure 14-6. Transmit Side D4 Timing
NOTE 1: RSER DATA IN CHANNELS 1, 5, 9, 13, 17, 21, 25, AND 29 ARE FORCED TO 1; TSER IGNORED DURING THESE CHANNELS.
NOTE 2: RSYNC IS IN THE OUTPUT MODE (RCR2.3 = 0).
NOTE 3: RSYNC IS IN THE INPUT MODE (RCR2.3 = 1).
NOTE 4: RCHBLK IS FORCED TO 1 IN THE SAME CHANNELS AS RSER (SEE NOTE 1).
NOTE 1: TSYNC IN THE FRAME MODE (TCR2.3 = 0) AND DOUBLE-WIDE FRAME SYNC IS NOT ENABLED (TCR2.4 = 0).
NOTE 2: TSYNC IN THE FRAME MODE (TCR2.3 = 0) AND DOUBLE-WIDE FRAME SYNC IS ENABLED (TCR2.4 = 1).
NOTE 3: TSYNC IN THE MULTIFRAME MODE (TCR2.3 = 1).
NOTE 4: TLINK DATA (S-BIT) IS SAMPLED DURING THE F-BIT POSITION OF EVEN FRAMES FOR INSERTION INTO THE OUTGOING T1
STREAM WHEN ENABLED VIA TCR1.2.
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Figure 14-7. Transmit Side ESF Timing
NOTE 1: TSYNC IN THE FRAME MODE (TCR2.3 = 0) AND DOUBLE-WIDE FRAME SYNC IS NOT ENABLED (TCR2.4 = 0).
NOTE 2: TSYNC IN THE FRAME MODE (TCR2.3 = 0) AND DOUBLE-WIDE FRAME SYNC IS ENABLED (TCR2.4 = 1).
NOTE 3: TSYNC IN THE MULTIFRAME MODE (TCR2.4 = 1).
NOTE 4: ZBTSI MODE DISABLED (TCR2.5 = 0).
NOTE 5: TLINK DATA (FDL BITS) IS SAMPLED DURING THE F-BIT TIME OF ODD FRAME AND INSERTED INTO THE OUTGOING T1 STREAM
IF ENABLED VIA TCR1.2.
NOTE 6: ZBTSI MODE IS ENABLED (TCR2.5 = 1).
NOTE 7: TLINK DATA (Z BITS) IS SAMPLED DURING THE F-BIT TIME OF FRAME 1, 5, 9, 13, 17, AND 21 AND INSERTED INTO THE
OUTGOING STREAM IF ENABLED VIA TCR1.2.
DS2151Q
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Figure 14-8. Transmit Side Boundary Timing with Elastic Store(s) Disabled
NOTE 1: TSYNC IS IN THE INPUT MODE (TCR2.2 = 0).
NOTE 2: TSYNC IS IN THE OUTPUT MODE (TCR2.2 = 1).
NOTE 3: TCHBLK IS PROGRAMMED TO BLOCK CHANNEL 1.
NOTE 4: SEE Figure 14-4 AND Figure 14-5 FOR DETAILS ON TIMING WITH THE TRANSMIT SIDE ELASTIC STORE ENABLED.
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Figure 14-9. Transmit Data Flow
DS2151Q
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15 DC CHARACTERISTICS
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground……………………………………………..-1.0V to +7.0V
Operating Temperature Range
Commercial…………………………………………………………...………..……...0°C to +70°C
Industrial…………………………………………………………………………….-40°C to +85°C
Storage Temperature ………………………………………………………………………-55°C to +125°C
Soldering Temperature...………………………………………..See IPC/JEDEC J-STD-020 Specification
This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation
sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect
reliability.
Table 15-1. Recommended DC Characteristics
(TA = 0°C to +70°C for DS2151Q, TA = -40°C to +85°C for DS2151QN.)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Logic 1 VIH 2.0 VDD + 0.3 V
Logic 0 VIL -0.3 +0.8 V
Supply VDD 4.75 5.25 V 1
Table 15-2. Capacitance
(TA = +25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Input Capacitance CIN 5 pF
Output Capacitance COUT 7 pF
Table 15-3. DC Characteristics
(VDD = 5V ±5%, TA = 0°C to +70°C for DS2151Q, TA = -40°C to +85°C for DS2151QN.)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Supply Current at 5V IDD 65 mA 2
Input Leakage IIL -1.0 +1.0
µA 3
Output Leakage ILO 1.0
µA 4
Output Current (2.4V) IOH -1.0 mA
Output Current (0.4V) IOL +4.0 mA
NOTES:
1) Applies to RVDD, TVDD, and DVDD.
2) TCLK = 1.544MHz.
3) 0V < VIN < VDD.
4) Applies to INT1 and INT1 when tri-stated.
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16 AC CHARACTERISTICS
Table 16-1. AC Characteristics—Parallel Port
(VDD = 5V ±5%, TA = 0°C to +70°C for DS2151Q, TA = -40°C to +85°C for DS2151QN.)
(See Figure 16-1, Figure 16-2, and Figure 16-3.)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Cycle Time tCYC 250 ns
Pulse Width, DS Low or RD
High PWEL 150 ns
Pulse Width, DS High or RD
Low PWEH 100 ns
Input Rise/Fall Times tR, tF 30 ns
R/ W Hold Time tRWH 10 ns
R/ W Setup Time before DS
High tRWS 50 ns
CS Setup Time before DS,
WR or RD Active tCS 20 ns
CS Hold Time tCH 0 ns
Read Data Hold Time tDHR 10 50 ns
Write Data Hold Time tDHW 0 ns
Muxed Address Valid to AS
or ALE Fall tASL 20 ns
Muxed Address Hold Time tAHL 10 ns
Delay Time DS, WR or RD
to AS or ALE Rise tASD 25 ns
Pulse Width AS or ALE High PWASH 40 ns
Delay Time, AS or ALE to
DS, WR or RD tASED 20 ns
Output Data Delay Time from
DS or RD tDDR 20 100 ns
Data Setup Time tDSW 80 ns
DS2151Q
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Figure 16-1. Intel Bus Read AC Timing
Figure 16-2. Intel Bus Write AC Timing
DS2151Q
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Figure 16-3. Motorola Bus AC Timing
DS2151Q
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Table 16-2. AC Characteristics—Receive Side
(VDD = 5V ±5%, TA = 0°C to +70°C for DS2151Q, TA = -40°C to +85°C for DS2151QN.)
(See Figure 16-4.)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
ACLKI/RCLK Period tCP 648 ns
tCH 230 324 ns
RCLK Pulse Width tCL 230 324 ns 1
tCH 115 ns
RCLK Pulse Width tCL 115 ns 2
tSP 648 ns 3
SYSCLK Period tSP 488 ns 4
tSH 75 ns
SYSCLK Pulse Width tSL 75
RSYNC Setup to SYSCLK
Falling tSU 25 tSH -5 ns
RSYNC Pulse Width tPW 50 ns
SYSCLK Rise/Fall Times tR, tF 25 ns
Delay RCLK or SYSCLK to
RSER Valid tDD 10 80 ns
Delay RCLK or SYSCLK to
RCHCLK tD1 10 90 ns
Delay RCLK or SYSCLK to
RCHBLK tD2 10 90 ns
Delay RCLK or SYSCLK to
RSYNC tD3 10 80 ns
Delay RCLK to RLCLK tD4 10 80 ns
Delay RCLK to RLINK Valid tD5 10 110 ns
NOTES:
1) Jitter attenuator enabled in the receive side path.
2) Jitter attenuator disabled or enabled in the transmit path.
3) SYSCLK = 1.544MHz.
4) SYSCLK = 2.048MHz.
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Figure 16-4. Receive Side AC Timing
NOTE 1: RSYNC IS IN THE OUTPUT MODE (RCR2.3 = 0).
NOTE 2: RSYNC IS IN THE INPUT MODE (RCR2.3 = 1).
NOTE 3: RLCLK AND RLINK ONLY HAVE A TIMING RELATIONSHIP TO RCLK.
NOTE 4: RCLK CAN EXHIBIT A SHORT HIGH TIME IF THE JITTER ATTENUATOR IS EITHER DISABLED OR IN THE TRANSMIT PATH.
DS2151Q
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Table 16-3. AC Characteristics—Transmit Side
(VDD = 5V ±5%, TA = 0°C to +70°C for DS2151Q, TA = -40°C to +85°C for DS2151QN.)
(See Figure 16-5.)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
TCLK Period tP 648 ns
tCH 75 ns
TCLK Pulse Width tCL 75 ns
TSER and TLINK Set up to
TCLK Falling tSU 25 ns 1
TSER and TLINK Hold from
TCLK Falling tHD 25 ns 1
TSYNC Set up to TCLK
Falling tSU 25 tCH -5
TSYNC Pulse Width tPW 50
TCLK Rise/Fall Times tR, tF 25 ns
Delay TCLK to TCHCLK tD1 10 60 ns
Delay TCLK to TCHBLK tD2 10 70 ns
Delay TCLK to TSYNC tD3 10 60 ns
Delay TCLK to TLCLK tD4 10 60 ns
NOTES:
1) If the transmit side elastic store is enabled, then TSER is sampled on the falling edge of SYSCLK and
the parameters tSU and tHD still apply.
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Figure 16-5. Transmit Side AC Timing
NOTE 1: TSYNC IS IN THE OUTPUT MODE (TCR2.2 = 1).
NOTE 2: TSYNC IS IN THE INPUT MODE (TCR2.2 = 0).
NOTE 3: TSER IS SAMPLED ON THE FALLING EDGE OF SYSCLK IF THE TRANSMIT SIDE ELASTIC STORE IS ENABLED.
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Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product.
No circuit patent licenses are implied. Maxim/Dallas Semiconductor reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2006 Maxim Integrated Products • Printed USA
The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor.
17 PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. The package number provided for
each package is a link to the latest package outline information.)
17.1 44-Pin PLCC (56-G4003-001)
