IDT723624L15PFG - Integrated Device Technology

DSC-3270/3

AUGUST 2001

IDT723624

IDT723634

IDT723644

CMOS SyncBiFIFOTM WITH BUS-MATCHING

256 x 36 x 2,

512 x 36 x 2,

1,024 x 36 x 2

IDT and the IDT logo are trademark of Integrated Device Technology, Inc. SyncBiFIFO is a trademark of Integrated Device Technology, Inc.

COMMERCIAL TEMPERATURE RANGE

FUNCTIONAL BLOCK DIAGRAM

FEATURES:

••

•Memory storage capacity:

IDT723624 – 256 x 36 x 2

IDT723634 – 512 x 36 x 2

IDT723644 – 1,024 x 36 x 2

••

•Clock frequencies up to 83 MHz (8 ns access time)

••

•Two independent clocked FIFOs buffering data in opposite

directions

••

•Select IDT Standard timing (using EFA, EFB, FFA, and FFB flags

functions) or First Word Fall Through Timing (using ORA, ORB,

IRA, and IRB flag functions)

••

•Programmable Almost-Empty and Almost-Full flags; each has

three default offsets (8, 16 and 64)

••

•Serial or parallel programming of partial flags

••

•Port B bus sizing of 36-bits (long word), 18-bits (word) and

9-bits (byte)

••

•Big- or Little-Endian format for word and byte bus sizes

••

•Master Reset clears data and configures FIFO, Partial Reset

clears data but retains configuration settings

••

•Mailbox bypass registers for each FIFO

••

•Free-running CLKA and CLKB may be asynchronous or coinci-

dent (simultaneous reading and writing of data on a single clock

edge is permitted)

••

•Auto power down minimizes power dissipation

••

•Available in space saving 128-pin Thin Quad Flatpack (TQFP)

••

•

Industrial temperature range (–40

°°

C to +85

°°

C) is available

Mail 1

Programmable Flag

Offset Registers

Input

RAM ARRAY

256 x 36

512 x 36

1,024 x 36

Write

Pointer

Read

Pointer

Status Flag

Logic

Input

Output

RAM ARRAY

256 x 36

512 x 36

1,024 x 36

Write

Pointer

Read

Pointer

Status Flag

Logic

CLKA

CSA

W/RA

ENA

MBA

Port-A

Control

Logic

FIFO1,

Mail1

Reset

Logic

MRS1

Mail 2

MBF2

CLKB

CSB

W/RB

ENB

MBB

SIZE

Port-B

Control

Logic

FIFO2,

Mail2

Reset

Logic

MRS2

MBF1

FIFO1

FIFO2

EFB/ORB

AEB

FFB/IRB

AFB

-B

FFA/IRA

AFA

SPM

FS0/SD

FS1/SEN

-A

EFA/ORA

AEA

3270 drw01

Output Bus-

Matching

Output

PRS2

PRS1

Timing

Mode FWFT

36 36

Input Bus-

Matching

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

PIN CONFIGURATION

TQFP (PK128-1, order code: PF)

TOP VIEW

DESCRIPTION:

The IDT723624/723634/723644 is a monolithic, high-speed, low-

power, CMOS bidirectional synchronous (clocked) FIFO memory which

supports clock frequencies up to 83 MHz and has read access times as fast as

8 ns. Two independent 256/512/1,024 x 36 dual-port SRAM FIFOs on board

each chip buffer data in opposite directions. FIFO data on Port B can be input

and output in 36-bit, 18-bit, or 9-bit formats with a choice of Big- or Little-Endian

configurations.

These devices are a synchronous (clocked) FIFO, meaning each port

employs a synchronous interface. All data transfers through a port are gated

to the LOW-to-HIGH transition of a port clock by enable signals. The clocks for

each port are independent of one another and can be asynchronous or

coincident. The enables for each port are arranged to provide a simple

bidirectional interface between microprocessors and/or buses with syn-

chronous control.

W/RACLKB

3270 drw02

ENA

CLKA

GND

A35

A34

A33

A32

Vcc

A31

A30

GND

A29

A28

A27

A26

A25

A24

A23

BE/FWFT

GND

A22

Vcc

A21

A20

A19

A18

GND

A17

A16

A15

A14

A13

Vcc

A12

GND

A11

A10

100

102

101

128

127

126

125

124

123

122

121

120

119

118

117

116

115

114

113

112

111

110

109

108

107

106

105

PRS2

Vcc

B35

B34

B33

B32

GND

B31

B30

B29

B28

B27

B26

Vcc

B25

B24

GND

B23

B22

B21

B20

B19

B18

GND

B17

B16

Vcc

B15

B14

B13

B12

GND

B11

B10

CSA

FFA/IRA

EFA/ORA

PRS1

Vcc

AFA

AEA

MBF2

MBA

MRS1

FS0/SD

GND

FS1/SEN

MRS2

MBB

MBF1

Vcc

AEB

AFB

EFB/ORB

FFB/IRB

GND

CSB

W/RB

ENB

GND

SPM

Vcc

GND

Vcc

104

103

INDEX

SIZE

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Communication between each port may bypass the FIFOs via two

mailbox registers. The mailbox register width matches the selected Port B bus

width. Each Mailbox register has a flag (MBF1 and MBF2) to signal when new

mail has been stored.

Two kinds of reset are available on these FIFOs: Master Reset and Partial

Reset. Master Reset initializes the read and write pointers to the first location

of the memory array, configures the FIFO for Big- or Little-Endian byte

arrangement and selects serial flag programming, parallel flag programming,

or one of three possible default flag offset settings, 8, 16 or 64. There are two

Master Reset pins, MRS1 and MRS2.

Partial Reset also sets the read and write pointers to the first location of the

memory. Unlike Master Reset, any settings existing prior to Partial Reset (i.e.,

programming method and partial flag default offsets) are retained. Partial Reset

is useful since it permits flushing of the FIFO memory without changing any

configuration settings. Each FIFO has its own, independent Partial Reset pin,

PRS1 and PRS2.

These devices have two modes of operation: In the IDT Standard mode,

the first word written to an empty FIFO is deposited into the memory array. A

read operation is required to access that word (along with all other words

residing in memory). In the First Word Fall Through mode (FWFT), the first

long-word (36-bit wide) written to an empty FIFO appears automatically on the

outputs, no read operation is required (nevertheless, accessing subsequent

words does necessitate a formal read request). The state of the BE/FWFT pin

during FIFO operation determines the mode in use.

Each FIFO has a combined Empty/Output Ready Flag (EFA/ORA and

EFB/ORB) and a combined Full/Input Ready Flag (FFA/IRA and FFB/IRB).

The EF and FF functions are selected in the IDT Standard mode. EF indicates

whether or not the FIFO memory is empty. FF shows whether the memory is

full or not. The IR and OR functions are selected in the First Word Fall Through

mode. IR indicates whether or not the FIFO has available memory locations.

OR shows whether the FIFO has data available for reading or not. It marks the

presence of valid data on the outputs.

Each FIFO has a programmable Almost-Empty flag (AEA and AEB) and

a programmable Almost-Full flag (AFA and AFB). AEA and AEB indicate when

a selected number of words remain in the FIFO memory. AFA and AFB indicate

when the FIFO contains more than a selected number of words.

FFA/IRA, FFB/IRB, AFA and AFB are two-stage synchronized to the port

clock that writes data into its array. EFA/ORA, EFB/ORB, AEA and AEB are

two-stage synchronized to the port clock that reads data from its array.

Programmable offsets for AEA, AEB, AFA and AFB are loaded in parallel using

Port A or in serial via the SD input. The Serial Programming Mode pin (SPM)

makes this selection. Three default offset settings are also provided. The AEA

and AEB threshold can be set at 8, 16 or 64 locations from the empty boundary

and the AFA and AFB threshold can be set at 8, 16 or 64 locations from the full

boundary. All these choices are made using the FS0 and FS1 inputs during

Master Reset.

Two or more devices may be used in parallel to create wider data

paths. If, at any time, the FIFO is not actively performing a function, the chip

will automatically power down. During the power down state, supply current

consumption (ICC) is at a minimum. Initiating any operation (by activating

control inputs) will immediately take the device out of the power down state.

The IDT723624/723634/723644 are characterized for operation from

0°C to 70°C. Industrial temperature range (-40°C to +85°C) is available. They

are fabricated using IDT’s high speed, submicron CMOS technology.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

PIN DESCRIPTIONS

Symbol Name I/O Description

A0-A35 Port A Data I/O 36-bit bidirectional data port for side A.

AEA Port A Almost- O Programmable Almost-Empty flag synchronized to CLKA. It is LOW when the number of words in FIFO2 is less

Empty Flag than or equal to the value in the Almost-Empty A Offset register, X2.

AEB Port B Almost- O Programmable Almost-Empty flag synchronized to CLKB. It is LOW when the number of words in FIFO1 is less

Empty Flag than or equal to the value in the Almost-Empty B Offset register, X1.

AFA Port A Almost- O Programmable Almost-Full flag synchronized to CLKA. It is LOW when the number of empty locations in FIFO1

Full Flag is less than or equal to the value in the Almost-Full A Offset register, Y1.

AFB Port B Almost- O Programmable Almost-Full flag synchronized to CLKB. It is LOW when the number of empty locations in FIFO2

Full Flag FIFO2 is less than or equal to the value in the Almost-Full B Offset register, Y2.

B0-B35 Port A Data I/O 36-bit bidirectional data port for side B.

BE/FWFT Big-Endian/ I This is a dual purpose pin. During Master Reset, a HIGH on BE will select Big Endian operation. In this case,

First Word depending on the bus size, the most significant byte or word on Port A is read from Port B first (A-to-B data

Fall Through flow) or written to Port B first (B-to-A data flow). A LOW on BE will select Little-Endian operation. In this case,

Select the least significant byte or word on Port A is read from Port B first (for A-to-B data flow) or written to Port B first

(B-to-A data flow). After Master Reset, this pin selects the timing mode. A HIGH on FWFT selects IDT

Standard mode, a LOW selects First Word Fall Through mode. Once the timing mode has been

selected, the level on FWFT must be static throughout device operation.

BM(1) Bus-Match I A HIGH on this pin enables either byte or word bus width on Port B, depending on the state of SIZE. A LOW

Select selects long word operation. BM works with SIZE and BE to select the bus size and endian arrangement for

(Port B) Port B. The level of BM must be static throughout device operation.

CLKA Port A Clock I CLKA is a continuous clock that synchronizes all data transfers through Port A and can be asynchronous or

coincident to CLKB. FFA/IRA, EFA/ORA, AFA, and AEA are all synchronized to the LOW-to-HIGH transition of

CLKA.

CLKB Port B Clock I CLKB is a continuous clock that synchronizes all data transfers through Port B and can be asynchronous or

coincident to CLKA. FFB/IRB, EFB/ORB, AFB, and AEB are synchronized to the LOW-to-HIGH transition of

CLKB.

CSA Port A Chip I CSA must be LOW to enable to LOW-to-HIGH transition of CLKA to read or write on Port A. The A0-A35

Select outputs are in the high-impedance state when CSA is HIGH.

CSB Port B Chip I CSB must be LOW to enable a LOW-to-HIGH transition of CLKB to read or write on Port B. The B0-B35

Select outputs are in the high-impedance state when CSB is HIGH.

EFA/ORA Port A Empty/ O This is a dual function pin. In the IDT Standard mode, the EFA function is selected. EFA indicates whether or

Output Ready not the FIFO2 memory is empty. In the FWFT mode, the ORA function is selected. ORA indicates the presence

Flag of valid data on A0-A35 outputs, available for reading. EFA/ORA is synchronized to the LOW-to-HIGH

transition of CLKA.

EFB/ORB Port B Empty/ O This is a dual function pin. In the IDT Standard mode, the EFB function is selected. EFB indicates whether or

Output Ready not the FIFO1 memory is empty. In the FWFT mode, the ORB function is selected. ORB indicates the presence

Flag of valid data on the B0-B35 outputs, available for reading. EFB/ORB is synchronized to the LOW-to-HIGH transition

of CLKB.

ENA Port A Enable I ENA must be HIGH to enable a LOW-to-HIGH transition of CLKA to read or write data on Port A.

ENB Port B Enable I ENB must be HIGH to enable a LOW-to-HIGH transition of CLKB to read or write data on Port B.

FFA/IRA Port A Full/ O This is a dual function pin. In the IDT Standard mode, the FFA function is selected. FFA indicates whether or

Input Read not the FIFO1 memory is full. In the FWFT mode, the IRA function is selected. IRA indicates whether or not

Flag there is space available for writing to the FIFO1 memory. FFA/IRA is synchronized to the LOW-to-HIGH

transition of CLKA.

FFB/IRB Port B Full/ O This is a dual function pin. In the IDT Standard mode, the FFB function is selected. FFB indicates whether or

Input Ready not the FIFO2 memory is full. In the

FWFT mode, the IRB function is selected. IRB indicates whether or not

Flag there

is space available for writing to the FIFO memory. FFB/IRB is synchronized to the LOW-to-HIGH transition

of CLKB.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Symbol Name I/O Description

FS1/SEN Flag Offset I FS1/SEN and FS0/SD are dual-purpose inputs used for flag offset register programming. During Master Reset,

Select 1/ FS1/SEN and FS0/SD, together with SPM, select the flag offset programming method. Three offset register

Serial Enable, programming methods are available: automatically load one of three preset values (8, 16, or 64), parallel load

from Port A, and serial load.

FS0/SD Flag Offset I

Select 0/ When serial load is selected for flag offset register programming, FS1/SEN is used as an enable synchronous to

Serial Data the LOW-to-HIGH transition of CLKA. When FS1/SEN is LOW, a rising edge on CLKA load the bit present on

FS0/SD into the X and Y registers. The number of bit writes required to program the offset registers is 32 for the

723624, 36 for the 723634, and 40 for the 723644. The first bit write stores the Y1 register MSB and the last bit

write stores the X2 register LSB.

MB A Port A Mailbox I A HIGH level on MBA chooses a mailbox register for a Port A read or write operation. When the A0-A35

Select outputs are active, a HIGH level on MBA selects data from the mail2 register for output and a LOW level selects

FIFO2 output register data for output.

MB B Port B Mailbox I A HIGH level on MBB chooses a mailbox register for a Port B read or write operation. When the B0-B35

Select outputs are active, a HIGH level on MBB selects data from the mail1 register for output and a LOW level selects

FIFO1 output register data for output.

MBF1 Mail1 Register O MBF1 is set LOW by a LOW-to-HIGH transition of CLKA that writes data to the mail1 register. Writes to the

Flag mail1 register are inhibited while MBF1 is LOW. MBF1 is set HIGH by a LOW-to-HIGH transition of CLKB when

a Port B read is selected and MBB is HIGH. MBF1 is set HIGH following either a Master or Partial Reset of

FIFO1.

MBF2 Mail2 Register O MBF2 is set LOW by a LOW-to-HIGH transition of CLKB that writes data to the mail2 register. Writes to the

Flag mail2 register are inhibited while MBF2 is LOW. MBF2 is set HIGH by a LOW-to-HIGH transition of CLKA when a

Port A read is selected and MBA is HIGH. MBF2 is set HIGH following either a Master or Partial Reset of

FIFO2.

MRS1 FIFO1 Master I A LOW on this pin initializes the FIFO1 read and write pointers to the first location of memory and sets the Port B

Reset output register to all zeroes. A LOW-to-HIGH transition on MRS1 selects the programming method (serial or parallel)

and one of three programmable flag default offsets for FIFO1 and FIFO2. It also configures Port B for bus size and

endian arrangement. Four LOW-to-HIGH transitions of CLKA and four LOW-to-HIGH transitions of CLKB must occur

while MRS1 is LOW.

MRS2 FIFO2 Master I A LOW on this pin initializes the FIFO2 read and write pointers to the first location of memory and sets the Port A

Reset output register to all zeroes. A LOW-to-HIGH transition on MRS2 toggled simultaneously with MRS1, selects the

programming method (serial or parallel) and one of the programmable flag default offsets for FIFO2. Four LOW-

to-HIGH transitions of CLKA and four LOW-to-HIGH transitions of CLKB must occur while MRS2 is LOW.

PRS1 FIFO1 Partial I A LOW on this pin initializes the FIFO1 read and write pointers to the first location of memory and sets the Port B

Reset output register to all zeroes. During Partial Reset, the currently selected bus size, endian arrangement, program

ming method (serial or parallel), and programmable flag settings are all retained.

PRS2 FIFO2 Partial I A LOW on this pin initializes the FIFO2 read and write pointers to the first location of memory and sets the Port A

Reset output register to all zeroes. During Partial Reset, the currently selected bus size, endian arrangement, program

ming method (serial or parallel), and programmable flag settings are all retained.

SIZE(1) Bus Size Select I A HIGH on this pin when BM is HIGH selects byte bus (9-bit) size on Port B. A LOW on this pin when BM is

HIGH selects word (18-bit) bus size. SIZE works with BM and BE to select the bus size and endian arrangement

for Port B. The level of SIZE must be static throughout device operation.

SPM(1) Serial Program- I A LOW on this pin selects serial programming of partial flag offsets. A HIGH on this pin selects parallel

ming Mode programming or default offsets (8, 16, or 64).

W/RA Port-A Write/ I A HIGH selects a write operation and a LOW selects a read operation on Port A for a LOW-to- HIGH transition of

Read Select CLKA. The A0-A35 outputs are in the HIGH impedance state when W/RA is HIGH.

W/RB Port-B Write/ I A LOW selects a write operation and a HIGH selects a read operation on Port B for a LOW-to-HIGH transition of

Read Select CLKB. The B0-B35 outputs are in the HIGH impedance state when W/RB is LOW.

PIN DESCRIPTIONS (CONTINUED)

NOTE:

1. BM, SIZE and SPM are not TTL compatible. These inputs should be tied to GND or VCC.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. Industrial temperature range product is available by special order.

2. All typical values are at VCC = 5V, TA = 25°C.

3. For additional ICC information, see Figure 1, Typical Characteristics: Supply Current (ICC) vs. Clock Frequency (fS).

4. Characterized values, not currently tested.

Symbol Rating Commercial Unit

VCC Supply Voltage Range –0.5 to 7 V

VI(2) Input Voltage Range –0.5 to VCC+0.5 V

VO(2) Output Voltage Range –0.5 to VCC+0.5 V

IIK Input Clamp Current (VI < 0 or VI > VCC) ±20 mA

IOK Output Clamp Current (VO = < 0 or VO > VCC) ±50 mA

IOUT Continuous Output Current (VO = 0 to VCC) ±50 mA

ICC Continuous Current Through VCC o r GN D ±400 mA

TSTG Storage Temperature Range –65 to 150 °C

NOTES:

1. Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only and functional operation of the device at

these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods

may affect device reliability.

2. The input and output voltage ratings may be exceeded provided the input and output current ratings are observed.

ABSOLUTE MAXIMUM RATINGS OVER OPERATING FREE-AIR TEMPERATURE

RANGE (Unless otherwise noted)(1)

Symbol Parameter Test Conditions Min. Typ.(2) Max. Unit

VOH Output Logic "1" Voltage VCC = 4.5V, IOH = –4 mA 2.4 — — V

VOL Output Logic "0" Voltage VCC = 4.5V, IOL = 8 mA — — 0.5 V

ILI Input Leakage Current (any Input) VCC = 5.5V, VI = VCC or 0 — — ±10 µA

ILO Output Leakage Current VCC = 5.5V, VO = VCC or 0 — — ±10 µA

ICC2(3) Standby Current (with CLKA and CLKB running) VCC = 5.5V, VI = VCC –0.2 V or 0 — — 8 mA

ICC3(3) Standby Current (no clocks running) VCC = 5.5V, VI = VCC –0.2 V or 0 — — 1 mA

CIN(4) Input Capacitance VI = 0, f = 1 MHz — 4 — pF

COUT(4) Output Capacitance VO = 0, f = 1 MHz — 8 — pF

ELECTRICAL CHARACTERISTICS OVER RECOMMENDED OPERATING

FREE-AIR TEMPERATURE RANGE (Unless otherwise noted)

(Commercial: VCC = 5V ± 10%, T A = 0°C to +70°C)

Symbol Parameter Min. Typ. Max. Unit

VCC Supply Voltage (Commercial) 4.5 5.0 5.5 V

VIH High-Level Input Voltage (Commercial) 2 — — V

VIL Low-Level Input Voltage (Commercial) — — 0.8 V

IOH High-Level Output Current (Commercial) — — –4 mA

IOL Low-Level Output Current (Commercial) — — 8 mA

TAOperating Free-Air Temperature (Commercial) 0 — 70 °C

RECOMMENDED OPERATING CONDITIONS

IDT723624

IDT723634

IDT723644

Commercial

tCLK= 12, 15ns

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

DETERMINING ACTIVE CURRENT CONSUMPTION AND POWER DISSIPATION

The ICC(f) current for the graph in Figure 1 was taken while simultaneously reading and writing a FIFO on the IDT723624/723634/723644 with

CLKA and CLKB set to fS. All data inputs and data outputs change state during each clock cycle to consume the highest supply current. Data

outputs were disconnected to normalize the graph to a zero capacitance load. Once the capacitance load per data-output channel and the number

of IDT723624/723634/723644 inputs driven by TTL HIGH levels are known, the power dissipation can be calculated with the equation below.

CALCULATING POWER DISSIPATION

With ICC(f) taken from Figure 1, the maximum power dissipation (PT) of these FIFOs may be calculated by:

PT = VCC x [ICC(f) + (N x ∆ICC x dc)] + Σ(CL x VCC2 X f o)

where:

N = number of used outputs = 36-bit (long word), 18-bit (word) or 9-bit (byte) bus size

∆ICC = increase in power supply current for each input at a TTL HIGH level

d c = duty cycle of inputs at a TTL HIGH level of 3.4 V

CL= output capacitance load

fo= switching frequency of an output

Figure 1. Typical Characteristics: Supply Current (ICC) vs. Clock Frequency (fS)

010 20 30 40 50 60 70

100

250

300

= 5.0V

 Clock Frequency  MHz

data

= 1/2 f

= 25°C

= 0pF

= 5.5V

3270 drw03

200

150 V

= 4.5V

80 90

CC(f)

Supply Current mA

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

TIMING REQUIREMENTS OVER RECOMMENDED RANGES OF SUPPLY

VOLTAGE AND OPERATING FREE-AIR TEMPERATURE

Symbol Parameter Min. Max. Min. Max. Unit

fSClock Frequency, CLKA or CLKB — 83 — 66.7 MH z

tCLK Clock Cycle Time, CLKA or CLKB 12 — 15 — ns

tCLKH Pulse Duration, CLKA or CLKB HIGH 5 — 6 — n s

tCLKL Pulse Duration, CLKA and CLKB LOW 5 — 6 — ns

tDS Setup Time, A0-A35 before CLKA↑ and B0-B35 before CLKB↑3—4—ns

tENS1 Setup Time, CSA and W/RA before CLKA↑; CSB and W/RB before CLKB↑4 — 4.5 — ns

tENS2 Setup Time ENA and MBA before CLKA↑; ENB and MBB before CLKB↑3 — 4.5 — ns

tRSTS Setup Time, MRS1, MRS2, PRS1, or PRS2 LOW before CLKA↑ or CLKB↑(2) 5—5—ns

tFSS Setup Time, FS0 and FS1 before MRS1 and MRS2 HIGH 7.5 — 7.5 — ns

tBES Setup Time, BE/FWFT before MRS1 and MRS2 HIGH 7.5 — 7.5 — ns

tSPMS Setup Time, SPM before MRS1 and MRS2 HIGH 7.5 — 7.5 — ns

tSDS Setup Time, FS0/SD before CLKA↑3—4—ns

tSENS Setup Time, FS1/SEN before CLKA↑3—4—ns

tFWS Setup Time, BE/FWFT before CLKA↑0—0—ns

tDH Hold Time, A0-A35 after CLKA↑ and B0-B35 after CLKB↑0.5 — 1 — ns

tENH Hold Time, CSA, W/RA, ENA, and MBA after CLKA↑; CSB, W/RB, ENB, and MBB 0.5 — 1 — ns

after CLKB↑

tRSTH Hold Time, MRS1, MRS2, PRS1 or PRS2 LOW after CLKA↑ or CLKB↑(2) 4—4—ns

tFSH Hold Time, FS0 and FS1 after MRS1 and MRS2 HIGH 2 — 2 — n s

tBEH Hold Time, BE/FWFT after MRS1 and MRS2 HIGH 2 — 2 — ns

tSPMH Hold Time, SPM after MRS1 and MRS2 HIGH 2 — 2 — ns

tSDH Hold Time, FS0/SD after CLKA↑0.5 — 1 — ns

tSENH Hold Time, FS1/SEN HIGH after CLKA↑0.5 — 1 — ns

tSPH Hold Time, FS1/SEN HIGH after MRS1 and MRS2 HIGH 2 — 2 — ns

tSKEW1(3) Skew Time between CLKA↑ and CLKB↑ for EFA/ORA, EFB/ORB, FFA/IRA, and FFB/IRB 5 — 7.5 — ns

tSKEW2(3,4) Skew Time between CLKA↑ and CLKB↑ for AEA, AEB, AFA, and AFB 12 — 12 — ns

NOTES:

1. Industrial temperature range is available by special order.

2. Requirement to count the clock edge as one of at least four needed to reset a FIFO.

3. Skew time is not a timing constraint for proper device operation and is only included to illustrate the timing relationship between CLKA cycle and CLKB cycle.

4. Design simulated, not tested.

(Commercial: VCC = 5V ± 10%, TA = 0 °C to +70°C)

Commercial

IDT723624L12 IDT723624L15

IDT723634L12 IDT723634L15

IDT723644L12 IDT723644L15

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

SWITCHING CHARACTERISTICS OVER RECOMMENDED RANGES OF SUPPLY

VOLTAGE AND OPERATING FREE-AIR TEMPERATURE, CL = 30PF

Symbol Parameter Min Max. Min. Max . Unit

tAAccess Time, CLKA↑ to A0-A35 and CLKB↑ to B0-B35 2 8 2 10 ns

tWFF Propagation Delay Time, CLKA↑ to FFA/IRA and CLKB↑ to FFB/IRB 2 8 2 8 ns

tREF Propagation Delay Time, CLKA↑ to EFA/ORA and CLKB↑ to EFB/ORB 1 8 1 8 ns

tPAE Propagation Delay Time, CLKA↑ to AEA and CLKB↑ to AEB 1818ns

tPAF Propagation Delay Time, CLKA) to AFA and CLKB↑ to AFB 1818ns

tPMF Propagation Delay Time, CLKA↑ to MBF1 LOW or MBF2 HIGH and CLKB↑ to MBF2 0808ns

LOW or MBF1 HIGH

tPMR Propagation Delay Time, CLKA↑ to B0-B35(2) and CLKB↑ to A0-A35(3) 28210ns

tMDV Propagation Delay Time, MBA to A0-A35 valid and MBB to B0-B35 valid 2 8 2 10 n s

tRSF Propagation Delay Time, MRS1 or PRS1 LOW to AEB LOW, AFA HIGH, and MBF1 110115ns

HIGH and MRS2 or PRS2 LOW to AEA LOW, AFB HIGH, and MBF2 HIGH

tEN Enable Time, CSA or W/RA LOW to A0-A35 Active and CSB LOW and W/RB HIGH to 2 6 2 10 n s

B0-B35 Active

tDIS Disable Time, CSA or W/RA HIGH to A0-A35 at high impedance and CSB HIGH or W/RB 1 6 1 8 ns

LOW to B0-B35 at HIGH impedance

NOTES:

1. Industrial temperature range is available by special order.

2. Writing data to the mail1 register when the B0-B35 outputs are active and MBB is HIGH.

3. Writing data to the mail2 register when the A0-A35 outputs are active and MBA is HIGH.

(Commercial: VCC = 5V ± 10%, T A = 0°C to +70°C) Commercial

IDT723624L12 IDT723624L15

IDT723634L12 IDT723634L15

IDT723644L12 IDT723644L15

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

SIGNAL DESCRIPTION

MASTER RESET (MRS1, MRS2)

After power up, a Master Reset operation must be performed by providing

a LOW pulse to MRS1 and MRS2 simultaneously. Afterwards, each of the two

FIFO memories of the IDT723624/723634/723644 undergoes a complete

reset by taking its associated Master Reset (MRS1, MRS2) input LOW for at

least four Port A Clock (CLKA) and four Port B Clock (CLKB) LOW-to-HIGH

transitions. The Master Reset inputs can switch asynchronously to the clocks.

A Master Reset initializes the associated read and write pointers to the first

location of the memory and forces the Full/Input Ready flag (FFA/IRA, FFB/

IRB) LOW, the Empty/Output Ready flag (EFA/ORA, EFB/ORB) LOW, the

Almost-Empty flag (AEA, AEB) LOW, and forces the Almost-Full flag (AFA,

AFB) HIGH. A Master Reset also forces the Mailbox Flag (MBF1, MBF2) of

the parallel mailbox register HIGH. After a Master Reset, the FIFO’s Full/Input

Ready flag is set HIGH after two write clock cycles. Then the FIFO is ready

to be written to.

A LOW-to-HIGH transition on a FlFO1 Master Reset (MRS1) input latches

the value of the Big-Endian (BE) input for determining the order by which bytes

are transferred through Port B. It also latches the values of the Flag Select (FS0,

FS1) and Serial Programming Mode (SPM) inputs for choosing the Almost-

Full and Almost-Empty offset programming method.

A LOW-to-HIGH transition on a FlFO2 Master Reset (MRS2) clears the

Flag Offset registers of FIFO2 (X2, Y2). A LOW-to-HIGH transition of the FIFO2

Master Reset (MRS2) together with the FIFO1 Master Reset (MRS1) input

latches the value of the Big-Endian (BE) input for the Port B and also latches

the values of the Flag Select (FS0, FS1) and Serial Programming Mode (SPM)

inputs for choosing the Almost-Full and Almost-Empty offset programming

method (for details see Table 1, Flag Programming, and the Programming

of the Almost-Empty and Almost-Full flags section). The relevant FIFO Master

Reset timing diagram can be found in Figure 3.

PARTIAL RESET (PRS1, PRS2)

Each of the two FIFO memories of these devices undergoes a limited reset

by taking its associated Partial Reset (PRS1, PRS2) input LOW for at least four

Port A Clock (CLKA) and four Port B Clock (CLKB) LOW-to-HIGH transitions.

The Partial Reset inputs can switch asynchronously to the clocks. A Partial

Reset initializes the internal read and write pointers and forces the Full/Input

Ready flag (FFA/IRA, FFB/IRB) LOW, the Empty/Output Ready flag (EFA/

ORA, EFB/ORB) LOW, the Almost-Empty flag (AEA, AEB) LOW, and the

Almost-Full flag (AFA, AFB) HIGH. A Partial Reset also forces the Mailbox Flag

(MBF1, MBF2) of the parallel mailbox register HIGH. After a Partial Reset, the

FIFO’s Full/Input Ready flag is set HIGH after two write clock cycles. Then the

FIFO is ready to be written to.

Whatever flag offsets, programming method (parallel or serial), and timing

mode (FWFT or IDT Standard mode) are currently selected at the time a Partial

Reset is initiated, those settings will be remain unchanged upon completion of

the reset operation. A Partial Reset may be useful in the case where

reprogramming a FIFO following a Master Reset would be inconvenient. See

Figure 4 for the Partial Reset timing diagram.

BIG-ENDIAN/FIRST WORD FALL THROUGH (BE/FWFT)

— ENDIAN SELECTION

This is a dual purpose pin. At the time of Master Reset, the BE select function

is active, permitting a choice of Big or Little-Endian byte arrangement for data

written to or read from Port B. This selection determines the order by which

bytes (or words) of data are transferred through this port. For the following

illustrations, assume that a byte (or word) bus size has been selected for Port

B. (Note that when Port B is configured for a long word size, the Big-Endian

function has no application and the BE input is a “don’t care”1.)

A HIGH on the BE/FWFT input when the Master Reset (MRS1 , MRS2)

inputs go from LOW to HIGH will select a Big-Endian arrangement. When data

is moving in the direction from Port A to Port B, the most significant byte (word)

of the long word written to Port A will be read from Port B first; the least significant

byte (word) of the long word written to Port A will be read from Port B last. When

data is moving in the direction from Port B to Port A, the byte (word) written to

Port B first will be read from Port A as the most significant byte (word) of the long

word; the byte (word) written to Port B last will be read from Port A as the least

significant byte (word) of the long word.

A LOW on the BE/FWFT input when the Master Reset (MRS1, MRS2)

inputs go from LOW to HIGH will select a Little-Endian arrangement. When data

is moving in the direction from Port A to Port B, the least significant byte (word)

of the long word written to Port A will be read from Port B first; the most significant

byte (word) of the long word written to Port A will be read from Port B last. When

data is moving in the direction from Port B to Port A, the byte (word) written to

Port B first will be read from Port A as the least significant byte (word) of the long

word; the byte (word) written to Port B last will be read from Port A as the most

significant byte (word) of the long word. Refer to Figure 2 for an illustration of

the BE function. See Figure 3 (Master Reset) for the Endian select timing

diagram.

— TIMING MODE SELECTION

After Master Reset, the FWFT select function is active, permitting a choice

between two possible timing modes: IDT Standard mode or First Word Fall

Through (FWFT) mode. Once the Master Reset (MRS1, MRS2) input is HIGH,

a HIGH on the BE/FWFT input during the next LOW-to-HIGH transition of CLKA

(for FIFO1) and CLKB (for FIFO2) will select IDT Standard mode. This mode

uses the Empty Flag function (EFA, EFB) to indicate whether or not there are

any words present in the FIFO memory. It uses the Full Flag function (FFA,

FFB) to indicate whether or not the FIFO memory has any free space for writing.

In IDT Standard mode, every word read from the FIFO, including the first, must

be requested using a formal read operation. Refer to Figure 3 (Master Reset)

for a First Word Fall Through select timing diagram.

Once the Master Reset (MRS1, MRS2) input is HIGH, a LOW on the BE/

FWFT input during the next LOW-to-HIGH transition of CLKA (for FIFO1) and

CLKB (for FIFO2) will select FWFT mode. This mode uses the Output Ready

function (ORA, ORB) to indicate whether or not there is valid data at the data

outputs (A0-A35 or B0-B35). It also uses the Input Ready function (IRA, IRB)

to indicate whether or not the FIFO memory has any free space for writing. In

the FWFT mode, the first word written to an empty FIFO goes directly to data

outputs, no read request necessary. Subsequent words must be accessed by

NOTE:

1 . Either a HIGH or LOW can be applied to a "don't care" input with no change to the logical operation of the FIFO. Nevertheless, inputs that are temporarily "don't care" (along with

unused inputs) must not be left open, rather they must be either HIGH or LOW.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

SPM FS1/SEN FS0/SD MRS1 MRS2 X1 AND Y1 REGlSTERS(1) X2 AND Y2 REGlSTERS(2)

HHH↑X64 X

HHH↑↑ 64 64

HHL↑X16 X

HHL↑↑ 16 16

HLH↑X8 X

HLH↑↑ 88

HLL↑↑ Parallel programming via Port A Parallel programming via Port A

LHL↑↑ Serial programming via SD Serial programming via SD

LHH↑↑ Reserved Reserved

LLH↑↑ Reserved Reserved

LLL↑↑ Reserved Reserved

performing a formal read operation. Refer to Figure 3 (Master Reset) for a First

Word Fall Through select timing diagram.

Following Master Reset, the level applied to the BE/FWFT input to choose

the desired timing mode must remain static throughout FIFO operation.

PROGRAMMING THE ALMOST-EMPTY AND ALMOST-FULL FLAGS

Four registers in the IDT723624/723634/723644 are used to hold the offset

values for the Almost-Empty and Almost-Full flags. The Port B Almost-Empty

flag (AEB) Offset register is labeled X1 and the Port A Almost-Empty flag (AEA)

Offset register is labeled X2. The Port A Almost-Full flag (AFA) Offset register

is labeled Y1 and the Port B Almost-Full flag (AFB) Offset register is labeled Y2.

The index of each register name corresponds to its FIFO number. The offset

registers can be loaded with preset values during the reset of a FIFO,

programmed in parallel using the FIFO’s Port A data inputs, or programmed

in serial using the Serial Data (SD) input (see Table 1).

SPM, FS0/SD and FS1/SEN function the same way in both IDT Standard

and FWFT modes.

— PRESET VALUES

To load a FIFO’s Almost-Empty flag and Almost-Full flag Offset registers with

one of the three preset values listed in Table 1, the Serial Program Mode (SPM)

and at least one of the flag-select inputs must be HIGH during the LOW-to-HIGH

transition of its Master Reset input (MRS1, MRS2). For example, to load the

preset value of 64 into X1 and Y1, SPM, FS0 and FS1 must be HIGH when

FlFO1 reset (MRS1) returns HIGH. Flag-offset registers associated with FIFO2

are loaded with one of the preset values in the same way with FIFO2 Master

Reset (MRS2), toggled simultaneously with FIFO1 Master Reset (MRS1). For

relevant preset value loading timing diagram, see Figure 3.

— PARALLEL LOAD FROM PORT A

To program the X1, X2, Y1, and Y2 registers from Port A, perform a Master

Reset on both FlFOs simultaneously with SPM HIGH and FS0 and FS1 LOW

during the LOW-to-HIGH transition of MRS1 and MRS2. After this reset is

complete, the first four writes to FIFO1 do not store data in the RAM but load

the offset registers in the order Y1, X1, Y2, X2. The Port A data inputs used by

the offset registers are (A7-A0), (A8-A0), or (A9-A0) for the IDT723624,

IDT723634, or IDT723644, respectively. The highest numbered input is used

as the most significant bit of the binary number in each case. Valid programming

values for the registers range from 1 to 252 for the IDT723624; 1 to 508 for the

IDT723634; and 1 to 1,020 for the IDT723644. After all the offset registers are

programmed from Port A, the Port B Full/Input Ready flag (FFB/IRB) is set

HIGH, and both FIFOs begin normal operation. Refer to Figure 5 for a timing

diagram illustration of parallel programming of the flag offset values.

— SERIAL LOAD

To program the X1, X2, Y1, and Y2 registers serially, initiate a Master Reset

with SPM LOW, FS0/SD LOW and FS1/SEN HIGH during the LOW-to-HIGH

transition of MRS1 and MRS2. After this reset is complete, the X and Y register

values are loaded bit-wise through the FS0/SD input on each LOW-to-HIGH

transition of CLKA that the FS1/SEN input is LOW. There are 32-, 36-, or 40-

bit writes needed to complete the programming for the IDT723624, IDT723634,

or IDT723644, respectively. The four registers are written in the order Y1, X1,

Y2, and finally, X2. The first-bit write stores the most significant bit of the Y1

(IDT723634), or 1 to 2,044 (IDT723644).

When the option to program the offset registers serially is chosen, the Port

A Full/Input Ready (FFA/IRA) flag remains LOW until all register bits are written.

FFA/IRA is set HIGH by the LOW-to-HIGH transition of CLKA after the last bit

is loaded to allow normal FIFO1 operation. The Port B Full/Input Ready (FFB/

IRB) flag also remains LOW throughout the serial programming process, until

all register bits are written. FFB/IRB is set HIGH by the LOW-to-HIGH transition

of CLKB after the last bit is loaded to allow normal FIFO2 operation.

See Figure 6 for Serial Programming of the Almost-Full Flag and Almost-

Empty Flag Offset Values (IDT Standard and FWFT Modes).

FIFO WRITE/READ OPERATION

The state of the Port A data (A0-A35) lines is controlled by Port A Chip Select

(CSA) and Port A Write/Read select (W/RA). The A0-A35 lines are in the High-

NOTES:

1 . X1 register holds the offset for AEB; Y1 register holds the offset for AFA.

2 . X2 register holds the offset for AEA; Y2 register holds the offset for AFB.

TABLE 1 — FLAG PROGRAMMING

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

TABLE 2 — PORT A ENABLE FUNCTION TABLE

CSA W/RA ENA MBA CLKA Data A (A0-A35) I/O PORT FUNCTION

H X X X X High-Impedance None

L H L X X Input None

LH HL ↑Input FIFO1 write

LH HH ↑Input Mail1 write

L L L L X Output None

LL HL↑Output FIFO2 read

L L L H X Output None

LL HH↑Output Mail2 read (set MBF2 HIGH)

CSB W/RB ENB MBB CLKB Data B (B0-B35) I/O PORT FUNCTION

H X X X X High-Impedance None

L L L X X Input None

LL HL↑Input FIFO2 write

LL HH↑Input Mail2 write

L H L L X Output None

LH HL↑Output FIFO1 read

L H L H X Output None

LH HH↑Output Mail1 read (set MBF1 HIGH)

TABLE 3 — PORT B ENABLE FUNCTION TABLE

impedance state when either CSA or W/RA is HIGH. The A0-A35 lines are

active outputs when both CSA and W/RA are LOW.

Data is loaded into FIFO1 from the A0-A35 inputs on a LOW-to-HIGH

transition of CLKA when CSA is LOW, W/RA is HIGH, ENA is HIGH, MBA is

LOW, and FFA/IRA is HIGH. Data is read from FIFO2 to the A0-A35 outputs

by a LOW-to-HIGH transition of CLKA when CSA is LOW, W/RA is LOW, ENA

is HIGH, MBA is LOW, and EFA/ORA is HIGH (see Table 2). FIFO reads and

writes on Port A are independent of any concurrent Port B operation.

The Port B control signals are identical to those of Port A with the exception

that the Port B Write/Read select (W/RB) is the inverse of the Port A Write/Read

select (W/RA). The state of the Port B data (B0-B35) lines is controlled by the

Port B Chip Select (CSB) and Port B Write/Read select (W/RB). The B0-B35

lines are in the high-impedance state when either CSB is HIGH or W/RB is

LOW. The B0-B35 lines are active outputs when CSB is LOW and W/RB is

HIGH.

Data is loaded into FIFO2 from the B0-B35 inputs on a LOW-to-HIGH

transition of CLKB when CSB is LOW, W/RB is LOW, ENB is HIGH, MBB is

LOW, and FFB/IRB is HIGH. Data is read from FIFO1 to the B0-B35 outputs

by a LOW-to-HIGH transition of CLKB when CSB is LOW, W/RB is HIGH, ENB

is HIGH, MBB is LOW, and EFB/ORB is HIGH (see Table 3). FIFO reads and

writes on Port B are independent of any concurrent Port A operation.

The setup and hold time constraints to the port clocks for the port Chip Selects

and Write/Read selects are only for enabling write and read operations and

are not related to high-impedance control of the data outputs. If a port enable

is LOW during a clock cycle, the port’s Chip Select and Write/Read select may

change states during the setup and hold time window of the cycle.

When operating the FIFO in FWFT mode and the Output Ready flag is LOW,

the next word written is automatically sent to the FIFO’s output register by the

LOW-to-HIGH transition of the port clock that sets the Output Ready flag HIGH.

When the Output Ready flag is HIGH, subsequent data is clocked to the output

registers only when a read is selected using the port’s Chip Select, Write/Read

select, Enable, and Mailbox select.

When operating the FIFO in IDT Standard mode, the first word will cause

the Empty Flag to change state on the second LOW-to-HIGH transition of the

Read clock. The data word will not be automatically sent to the output register.

Instead, data residing in the FIFO’s memory array is clocked to the output

select, Enable, and Mailbox select. Write and Read timing diagrams for Port

A can be found in Figure 7 and 14. Relevant Port B Write and Read cycle timing

diagrams together with Bus-Matching and Endian select operations can be

found in Figures 8 through 13.

SYNCHRONIZED FIFO FLAGS

Each FIFO is synchronized to its port clock through at least two flip-flop

stages. This is done to improve flag-signal reliability by reducing the probability

of metastable events when CLKA and CLKB operate asynchronously to one

another. EFA/ORA, AEA, FFA/IRA, and AFA are synchronized to CLKA.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Synchronized Synchronized

Number of Words in FIFO Memory(1,2) to CLKA to CLKB

IDT723624(3) IDT723634(3) IDT723644(3) EFA/ORA AEA AFB FFB/IRB

000LLHH

1 to X2 1 to X2 1 to X2 H L H H

(X2+1) to [256-(Y2+1)] (X2+1) to [512-(Y2+1)] (X2+1) to [1,024-(Y2+1)] H H H H

(256-Y2) to 255 (512-Y2) to 511 (1,024-Y2) to 1,023 H H L H

256 512 1,024 H H L L

TABLE 4 — FIFO1 FLAG OPERATION (IDT Standard and FWFT modes)

TABLE 5 — FIFO2 FLAG OPERATION (IDT Standard and FWFT modes)

Synchronized Synchronized

Number of Words in FIFO Memory(1,2) to CLKB to CLKA

IDT723624(3) IDT723634(3) IDT723644(3) EFB/ORB AEB AFA FFA/IRA

000LLHH

1 to X1 1 to X1 1 to X1 H L H H

(X1+1) to [256-(Y1+1)] (X1+1) to [512-(Y1+1)] (X1+1) to [1,024-(Y1+1)] H H H H

(256-Y1) to 255 (512-Y1) to 511 (1,024-Y1) to 1,023 H H L H

256 512 1,024 H H L L

EFB/ORB, AEB, FFB/IRB, and AFB are synchronized to CLKB. Tables 4 and

5 show the relationship of each port flag to FIFO1 and FIFO2.

EMPTY/OUTPUT READY FLAGS (EFA/ORA, EFB/ORB)

These are dual purpose flags. In the FWFT mode, the Output Ready (ORA,

ORB) function is selected. When the Output Ready flag is HIGH, new data is

present in the FIFO output register. When the Output Ready flag is LOW, the

previous data word is present in the FIFO output register and attempted FIFO

reads are ignored.

In the IDT Standard mode, the Empty Flag (EFA, EFB) function is selected.

When the Empty Flag is HIGH, data is available in the FIFO’s RAM memory

for reading to the output register. When the Empty Flag is LOW, the previous

data word is present in the FIFO output register and attempted FIFO reads are

ignored.

The Empty/Output Ready flag of a FIFO is synchronized to the port clock

that reads data from its array. For both the FWFT and IDT Standard modes,

the FIFO read pointer is incremented each time a new word is clocked to its

output register. The state machine that controls an Output Ready flag monitors

a write pointer and read pointer comparator that indicates when the FIFO

memory status is empty, empty+1, or empty+2.

In FWFT mode, from the time a word is written to a FIFO, it can be shifted

to the FIFO output register in a minimum of three cycles of the Output Ready

flag synchronizing clock. Therefore, an Output Ready flag is LOW if a word in

memory is the next data to be sent to the FlFO output register and three cycles

of the port Clock that reads data from the FIFO have not elapsed since the time

the word was written. The Output Ready flag of the FIFO remains LOW until

the third LOW-to-HIGH transition of the synchronizing clock occurs, simulta-

neously forcing the Output Ready flag HIGH and shifting the word to the FIFO

output register.

In IDT Standard mode, from the time a word is written to a FIFO, the Empty

Flag will indicate the presence of data available for reading in a minimum of two

cycles of the Empty Flag synchronizing clock. Therefore, an Empty Flag is LOW

if a word in memory is the next data to be sent to the FlFO output register and

two cycles of the port Clock that reads data from the FIFO have not elapsed

since the time the word was written. The Empty Flag of the FIFO remains LOW

until the second LOW-to-HIGH transition of the synchronizing clock occurs,

forcing the Empty Flag HIGH; only then can data be read.

A LOW-to-HIGH transition on an Empty/Output Ready flag synchronizing

clock begins the first synchronization cycle of a write if the clock transition occurs

NOTES:

1. When a word loaded to an empty FIFO is shifted to the output register, its previous FIFO memory location is free.

2. Data in the output register does not count as a "word in FIFO memory". Since in FWFT mode, the first word written to an empty FIFO goes unrequested to the output register

(no read operation necessary), it is not included in the FIFO memory count.

3. X1 is the Almost-Empty offset for FIFO1 used by AEB. Y1 is the Almost-Full offset for FIFO1 used by AFA. Both X1 and Y1 are selected during a FIFO1 reset or port A programming.

4. The ORB and IRA functions are active during FWFT mode; the EFB and FFA functions are active in IDT Standard mode.

NOTES:

1. When a word loaded to an empty FIFO is shifted to the output register, its previous FIFO memory location is free.

2. Data in the output register does not count as a "word in FIFO memory". Since in FWFT mode, the first word written to an empty FIFO goes unrequested to the output register

(no read operation necessary), it is not included in the FIFO memory count.

3. X2 is the Almost-Empty offset for FIFO2 used by AEA. Y2 is the Almost-Full offset for FIFO2 used by AFB. Both X2 and Y2 are selected during a FIFO2 reset or port A programming.

4. The ORA and IRB functions are active during FWFT mode; the EFA and FFB functions are active in IDT Standard mode.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

at time tSKEW1 or greater after the write. Otherwise, the subsequent clock cycle

can be the first synchronization cycle (see Figures 15, 16, 17, and 18).

FULL/INPUT READY FLAGS (FFA/IRA, FFB/IRB)

This is a dual purpose flag. In FWFT mode, the Input Ready (IRA and IRB)

function is selected. In IDT Standard mode, the Full Flag (FFA and FFB)

function is selected. For both timing modes, when the Full/Input Ready flag is

HIGH, a memory location is free in the FIFO to receive new data. No memory

locations are free when the Full/Input Ready flag is LOW and attempted writes

to the FIFO are ignored.

The Full/Input Ready flag of a FlFO is synchronized to the port clock that

writes data to its array. For both FWFT and IDT Standard modes, each time

a word is written to a FIFO, its write pointer is incremented. The state machine

that controls a Full/Input Ready flag monitors a write pointer and read pointer

comparator that indicates when the FlFO memory status is full, full-1, or full-2.

From the time a word is read from a FIFO, its previous memory location is ready

to be written to in a minimum of two cycles of the Full/Input Ready flag

synchronizing clock. Therefore, an Full/Input Ready flag is LOW if less than

two cycles of the Full/Input Ready flag synchronizing clock have elapsed since

the next memory write location has been read. The second LOW-to-HIGH

transition on the Full/Input Ready flag synchronizing clock after the read sets

the Full/Input Ready flag HIGH.

A LOW-to-HIGH transition on a Full/Input Ready flag synchronizing clock

begins the first synchronization cycle of a read if the clock transition occurs at

time tSKEW1 or greater after the read. Otherwise, the subsequent clock cycle

can be the first synchronization cycle (see Figures 19, 20, 21, and 22).

ALMOST-EMPTY FLAGS (AEA, AEB)

The Almost-Empty flag of a FIFO is synchronized to the port clock that reads

data from its array. The state machine that controls an Almost-Empty flag

monitors a write pointer and read pointer comparator that indicates when the

FIFO memory status is almost-empty, almost-empty+1, or almost-empty+2.

The almost-empty state is defined by the contents of register X1 for AEB and

FIFO reset, programmed from Port A, or programmed serially (see Almost-

Empty flag and Almost-Full flag offset programming section). An Almost-

Empty flag is LOW when its FIFO contains X or less words and is HIGH when

its FIFO contains (X+1) or more words. A data word present in the FIFO output

Two LOW-to-HIGH transitions of the Almost-Empty flag synchronizing clock

are required after a FIFO write for its Almost-Empty flag to reflect the new level

of fill. Therefore, the Almost-Full flag of a FIFO containing (X+1) or more words

remains LOW if two cycles of its synchronizing clock have not elapsed since

the write that filled the memory to the (X+1) level. An Almost-Empty flag is set

HIGH by the second LOW-to-HIGH transition of its synchronizing clock after

the FIFO write that fills memory to the (X+1) level. A LOW-to-HIGH transition

of an Almost-Empty flag synchronizing clock begins the first synchronization

cycle if it occurs at time tSKEW2 or greater after the write that fills the FIFO to (X+1)

words. Otherwise, the subsequent synchronizing clock cycle may be the first

synchronization cycle. (See Figures 23 and 24).

ALMOST-FULL FLAGS (AFA, AFB)

The Almost-Full flag of a FIFO is synchronized to the port clock that writes

data to its array. The state machine that controls an Almost-Full flag monitors

a write pointer and read pointer comparator that indicates when the FIFO

memory status is almost-full, almost-full-1, or almost-full-2. The almost-full state

is defined by the contents of register Y1 for AFA and register Y2 for AFB. These

registers are loaded with preset values during a FlFO reset, programmed from

Port A, or programmed serially (see Almost-Empty flag and Almost-Full flag

offset programming section). An Almost-Full flag is LOW when the number of

words in its FIFO is greater than or equal to (256-Y), (512-Y), or (1,024-Y)

for the IDT723624, IDT723634, or IDT723644 respectively. An Almost-Full

flag is HIGH when the number of words in its FIFO is less than or equal to [256-

(Y+1)], [512-(Y+1)], or [1,024-(Y+1)] for the IDT723624, IDT723634, or

IDT723644 respectively. Note that a data word present in the FIFO output

Two LOW-to-HIGH transitions of the Almost-Full flag synchronizing clock

are required after a FIFO read for its Almost-Full flag to reflect the new level

of fill. Therefore, the Almost-Full flag of a FIFO containing [256/512/1,024-

(Y+1)] or less words remains LOW if two cycles of its synchronizing clock have

not elapsed since the read that reduced the number of words in memory to [256/

512/1,024-(Y+1)]. An Almost-Full flag is set HIGH by the second LOW-to-HIGH

transition of its synchronizing clock after the FIFO read that reduces the number

of words in memory to [256/512/1,024-(Y+1)]. A LOW-to-HIGH transition of

an Almost-Full flag synchronizing clock begins the first synchronization cycle

if it occurs at time tSKEW2 or greater after the read that reduces the number of

words in memory to [256/512/1,024-(Y+1)]. Otherwise, the subsequent

synchronizing clock cycle may be the first synchronization cycle (see Figures

25 and 26).

MAILBOX REGISTERS

Each FIFO has a 36-bit bypass register to pass command and control

information between Port A and Port B without putting it in queue. The Mailbox

select (MBA, MBB) inputs choose between a mail register and a FIFO for a

port data transfer operation. The usable width of both the Mail1 and Mail2

registers matches the selected bus size for Port B.

A LOW-to-HIGH transition on CLKA writes data to the Mail 1 Register when

a Port A write is selected by CSA, W/RA, and ENA with MBA HIGH. If the

selected Port B bus size is also 36 bits, then the usable width of the Mail1 register

employs data lines A0-A35. If the selected Port B bus size is 18 bits, then the

usable width of the Mail1 Register employs data lines A0-A17. (In this case,

A18-A35 are don’t care inputs.) If the selected Port B bus size is 9 bits, then

the usable width of the Mail1 Register employs data lines A0-A8. (In this case,

A9-A35 are don’t care inputs.)

A LOW-to-HIGH transition on CLKB writes B0-B35 data to the Mail2

HIGH. If the selected Port B bus size is also 36 bits, then the usable width of

the Mail2 employs data lines B0-B35. If the selected Port B bus size is 18 bits,

then the usable width of the Mail2 Register employs data lines B0-B17. (In this

case, B18-B35 are don’t care inputs.) If the selected Port B bus size is 9 bits,

then the usable width of the Mail1 Register employs data lines B0-B8. (In this

case, B9-B35 are don’t care inputs.)

Writing data to a mail register sets its corresponding flag (MBF1 or MBF2)

LOW. Attempted writes to a mail register are ignored while the mail flag is LOW.

When data outputs of a port are active, the data on the bus comes from the

FIFO output register when the port Mailbox select input is LOW and from the

mail register when the port Mailbox select input is HIGH.

The Mail1 Register Flag (MBF1) is set HIGH by a LOW-to-HIGH transition

on CLKB when a Port B read is selected by CSB, W/RB, and ENB with MBB

HIGH. For a 36-bit bus size, 36 bits of mailbox data are placed on B0-B35. For

an 18-bit bus size, 18 bits of mailbox data are placed on B0-B17. (In this case,

B18-B35 are indeterminate.) For a 9-bit bus size, 9 bits of mailbox data are

placed on B0-B8. (In this case, B9-B35 are indeterminate.)

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

The Mail2 Register Flag (MBF2) is set HIGH by a LOW-to-HIGH transition

on CLKA when a Port A read is selected by CSA, W/RA, and ENA with MBA

HIGH.

For a 36-bit bus size, 36 bits of mailbox data are placed on A0-A35. For

an 18-bit bus size, 18 bits of mailbox data are placed on A0-A17. (In this case,

A18-A35 are indeterminate.) For a 9-bit bus size, 9 bits of mailbox data are

placed on A0-A8. (In this case, A9-A35 are indeterminate.)

The data in a mail register remains intact after it is read and changes only

when new data is written to the register. The Endian select feature has no effect

on mailbox data. For mail register and Mail Register flag timing diagrams, see

Figure 27 and 28.

BUS SIZING

The Port B bus can be configured in a 36-bit long word, 18-bit word, or

9-bit byte format for data read from FIFO1 or written to FIFO2. The levels

applied to the Port B Bus Size select (SIZE) and the Bus-Match select (BM)

determine the Port B bus size. These levels should be static throughout FIFO

operation. Both bus size selections are implemented at the completion of Master

Reset, by the time the Full/Input Ready flag is set HIGH, as shown in Figure

2. Two different methods for sequencing data transfer are available for Port

B when the bus size selection is either byte- or word-size. They are referred

to as Big-Endian (most significant byte first) and Little-Endian (least significant

byte first). The level applied to the Big-Endian select (BE) input during the LOW-

to-HIGH transition of MRS1 and MRS2 selects the endian method that will be

active during FIFO operation. BE is a don’t care input when the bus size

selected for Port B is long word. The endian method is implemented at the

completion of Master Reset, by the time the Full/Input Ready flag is set HIGH,

as shown in Figure 2.

Only 36-bit long word data is written to or read from the two FIFO memories

on the IDT723624/723634/723644. Bus-matching operations are done after

data is read from the FIFO1 RAM and before data is written to the FIFO2 RAM.

These bus-matching operations are not available when transferring data via

mailbox registers. Furthermore, both the word- and byte-size bus selections

limit the width of the data bus that can be used for mail register operations. In

this case, only those byte lanes belonging to the selected word- or byte-size

bus can carry mailbox data. The remaining data outputs will be indeterminate.

The remaining data inputs will be don’t care inputs. For example, when a word-

size bus is selected, then mailbox data can be transmitted only between A0-

A17 and B0-B17. When a byte-size bus is selected, then mailbox data can be

transmitted only between A0-A8 and B0-B8. (See Figures 27 and 28).

BUS-MATCHING FIFO1 READS

Data is read from the FIFO1 RAM in 36-bit long word increments. If a long

word bus size is implemented, the entire long word immediately shifts to the

FIFO1 output register. If byte or word size is implemented on Port B, only the

first one or two bytes appear on the selected portion of the FIFO1 output register,

with the rest of the long word stored in auxiliary registers. In this case, subsequent

FIFO1 reads output the rest of the long word to the FIFO1 output register in the

order shown by Figure 2.

When reading data from FIFO1 in byte or word format, the unused B0-B35

outputs are indeterminate.

BUS-MATCHING FIFO2 WRITES

Data is written to the FIFO2 RAM in 36-bit long word increments. Data written

to FIFO2 with a byte or word bus size stores the initial bytes or words in auxiliary

registers. The CLKB rising edge that writes the fourth byte or the second word

of long word to FIFO2 also stores the entire long word in the FIFO2 memory.

The bytes are arranged in the manner shown in Figure 2.

When writing data to FIFO2 in byte or word format, the unused B0-B35 inputs

are don't care inputs.

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 2. Bus Sizing

A35A27 A26A18 A17A9 A8A0

B35B27 B26B18 B17B9 B8B0

(a) LONG WORD SIZE

(b) WORD SIZE  BIG ENDIAN

(d) BYTE SIZE  BIG-ENDIAN

Write to FIFO1/

Read from FIFO2

Read from FIFO1/

Write to FIFO2

1st: Read from FIFO1/

Write to FIFO2

BE BM SIZE

H H L

L H L

H H H

X L X

BYTE ORDER ON PORT A:

B35B27 B26B18 B17B9 B8B0

BE BM SIZE

2nd: Read from FIFO1/

Write to FIFO2

3rd: Read from FIFO1/

Write to FIFO2

4th: Read from FIFO1/

Write to FIFO2

B35B27 B26B18 B17B9 B8B0

1st: Read from FIFO1/

Write to FIFO2

1st: Read from FIFO1/

Write to FIFO2

2nd: Read from FIFO1/

Write to FIFO2

2nd: Read from FIFO1/

Write to FIFO2

B35B27 B26B18 B17B9 B8B0

(e) BYTE SIZE  LITTLE-ENDIAN

1st: Read from FIFO1/

Write to FIFO2

BE BM SIZE

L H H

2nd: Read from FIFO1/

Write to FIFO2

3rd: Read from FIFO1/

Write to FIFO2

4th: Read from FIFO1/

Write to FIFO2

B35B27 B26B18 B17B9 B8B0

3270 drw 04

BYTE ORDER ON PORT B:

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. Partial Reset is performed in the same manner for FIFO2.

2. MRS1 must be HIGH during Partial Reset.

3. If BE/FWFT is HIGH, then EFB/ORB will go LOW one CLKB cycle earlier than in this case where BE/FWFT is LOW.

Figure 3. FIFO1 Master Reset and Loading X1 and Y1 with a Preset Value of Eight(1) (IDT Standard and FWFT Modes)

Figure 4. FIFO1 Partial Reset(1) (IDT Standard and FWFT Modes)

NOTES:

1 . FIFO2 (MRS2) Master Reset is performed in the same manner to load X2 and Y2 with a preset value. For FIFO2 Master Reset (MRS1) must toggle simultaneously with MRS2.

2. PRS1 must be HIGH during Master Reset.

3. If BE/FWFT is HIGH, then EFB/ORB will go LOW one CLKB cycle earlier than the case where BE/FWFT is LOW.

CLKA

MRS1

FFA/IRA

AEB

AFA

MBF1

CLKB

EFB/ORB

FS1,FS0

3270 drw05

RSTS

RSTH

FSH

FSS

WFF

REF

RSF

0,1

RSF

BE/FWFT

SPM

FWFT

BES

SPMS

BEH

SPMH

FWS

(3)

CLKA

PRS1

FFA/IRA

AEB

AFA

MBF1

CLKB

EFB/ORB

3270 drw06

RSTS

RSTH

WFF

REF(3)

RSF

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 6. Serial Programming of the Almost-Full Flag and Almost-Empty Flag Offset Values (IDT Standard and FWFT Modes)

Figure 5. Parallel Programming of the Almost-Full Flag and Almost-Empty Flag Offset Values after Reset (IDT Standard and FWFT Modes)

NOTES:

1. tSKEW1 is the minimum time between the rising CLKA edge and a rising CLKB edge for FFB/IRB to transition HIGH in the next cycle. If the time between the rising edge of CLKA

and rising edge of CLKB is less than tSKEW1, then FFB/IRB may transition HIGH one CLKB cycle later than shown.

2. It is not necessary to program offset register bits on consecutive clock cycles. FIFO write attempts are ignored until FFA/IRA and FFB/IRB is set HIGH.

3. Programmable offsets are written serially to the SD input in the order AFA offset (Y1), AEB offset (X1), AFB offset (Y2), and AEA offset (X2).

NOTES:

1. tSKEW1 is the minimum time between the rising CLKA edge and a rising CLKB edge for FFB/IRB to transition HIGH in the next cycle. If the time between the rising edge of CLKA

and rising edge of CLKB is less than tSKEW1, then FFB/IRB may transition HIGH one CLKB cycle later than shown.

2. CSA=LOW, W/RA=HIGH,MBA=LOW. It is not necessary to program offset register on consecutive clock cycles.

3270 drw07

CLKA

MRS1,

MRS2

FFA/IRA

CLKB

FFB/IRB

A0-A35

FS1,FS0

ENA

tFSH

tWFF

tENHtENS2 tSKEW1

tDS tDH

tWFF

0,0

AFA Offset

(Y1)

AEB Offset

(X1)

AFB Offset

(Y 2)

AEA Offset

(X 2) First Word to FIFO1

(1)

tFSH

tFSS

SPM

tFSS

CLKA

FFA/IRA

SENS

SENH

FS0/SD

(3)

SPH

SENS

SENH

FSS

WFF

FS1/SEN

AEA Offset

(X2) LSB

SDS

SDH

SDS

SDH

AFA Offset

(Y1) MSB

MRS1,

MRS2

3270 drw08

FSS

FSH

CLKB 4

SPM

FFB/IRB

WFF

SKEW(1)

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTE:

1. Written to FIFO1.

Figure 7. Port A Write Cycle Timing for FIFO1 (IDT Standard and FWFT Modes)

DATA SIZE TABLE FOR LONG-WORD WRITES TO FIFO2

Figure 8. Port B Long-Word Write Cycle Timing for FIFO2 (IDT Standard and FWFT Modes)

SIZE MODE(1) DATA WRITTEN TO FIFO2 DATA READ FROM FIFO2

BM SIZE BE B35-B27 B26-B18 B17-B9 B8-B0 A35-A27 A26-A18 A17-A9 A8-A0

LXXABCDABCD

NOTE:

1. BE is selected at Master Reset: BM and SIZE must be static throughout device operation.

NOTE:

1. Written to FIFO2.

3270 drw09

CLKA

FFA/IRA

ENA

A0 - A35

MBA

CSA

W/RA

tCLKH tCLKL

tCLK

tDS

tENH

tDH

(1)

tENH tENH

tENS2

No Operation

HIGH

tENS2

tENS1

3270 drw10

CLKB

FFB/IRB

ENB

B0-B35

MBB

CSB

W/RB

tCLK

tCLKH tCLKL

tENH

tDH

(1)

tDS

tENH

tENH tENS2

No Operation

tENS2

tENS1

tENS2

HIGH

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

SIZE MODE(1) WRITE NO. DATA WRITTEN TO FIFO2 DATA READ FROM FIFO2

BM SIZE BE B17-B9 B8-B0 A35-A27 A26-A18 A17-A9 A8-A0

HLH ABCD

HLL ABCD

DATA SIZE TABLE FOR WORD WRITES TO FIFO2

Figure 9. Port B Word Write Cycle Timing for FIFO2 (IDT Standard and FWFT Modes)

NOTE:

1. BE is selected at Master Reset; BM and SIZE must be static throughout device operation.

SIZE MODE(1) WRITE DATA WRITTEN DATA READ FROM FIFO2

NO. TO FIFO2

BM SIZE BE B8-B0 A35-A27 A26-A18 A17-A9 A8-A0

HHH A B C D

HHL A B C D

Figure 10. Port B Byte Write Cycle Timing for FIFO2 (IDT Standard and FWFT Modes)

NOTE:

1. BE is selected at Master Reset; BM and SIZE must be static throughout device operation.

CLKB

ENB

tENH tENH

FFB/IRB

W/RB

CSB

tENH

HIGH

3270 drw11

B0-B17

tENH

MBB

tDH

tDS

tENS2tENS2

tENS1

1AB

2CD

1CD

2AB

FFB/IRB

CSB

W/RB

CLKB

tENHtENS2

ENB

3270 drw12

HIGH

B0-B8

tENS2 tENH

tENS2

tENH

tDS tDH

tENS1

tENH

MBB

DATA SIZE TABLE FOR BYTE WRITES TO FIFO2

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

SIZE MODE(1) DATA WRITTEN TO FIFO1 READ NO. DATA READ FROM FIFO1

BM SIZE BE A35-A27 A26-A18 A17-A9 A8-A0 B17-B9 B8-B0

HLHA B C D1A B

2CD

HL LA B C D1CD

2AB

DATA SIZE TABLE FOR WORD READS FROM FIFO1

Figure 12. Port-B Word Read Cycle Timing for FIFO1 (IDT Standard and FWFT Modes)

NOTE:

1. BE is selected at Master Reset; BM and SIZE must be static throughout device operation .

SIZE MODE(1) DATA WRITTEN TO FIFO1 DATA READ FROM FIFO1

BM SIZE BE A35-A27 A26-A18 A17-A9 A8-A0 B35-B27 B26-B18 B17-B9 B8-B0

LXXAB CD A B CD

NOTE:

1. Read From FIFO1.

DATA SIZE TABLE FOR FIFO LONG-WORD READS FROM FIFO1

Figure 11. Port B Long-Word Read Cycle Timing for FIFO1 (IDT Standard and FWFT Modes)

NOTE:

1. BE is selected at Master Reset; BM and SIZE must be static throughout device operation.

NOTE:

1. Unused word B18-B35 are indeterminate for word size reads.

3270 drw13

CLKB

EFB/ORB

ENB

MBB

CSB

W/RB

CLK

CLKH

CLKL

ENS2

MDV

ENH

ENS2

ENH

W1 W2 W3

(1) (1)

ENH

DIS

No Operation

B0-B35

(FWFT Mode)

DIS

Previous Data

B0-B35

(Standard Mode)

MDV

OR t

(1)

HIGH

ENS2

CLKB

ENB

EFB/ORB

W/RB

CSB

HIGH

3270 drw14

B0-B17

(Standard Mode)

B0-B17

(FWFT Mode)

Previous Data

tENS2 tENH

No Operation

MBB

tEN

tMDV

tEN tMDV

tDIS

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

DATA SIZE TABLE FOR BYTE READS FROM FIFO1

SIZE MODE(1) DATA WRITTEN TO FIFO1 READ NO. DATA READ

FROM FIFO1

BM SIZE BE A35-A27 A26-A18 A17-A9 A8-A0 B8-B0

HH H A B C D

HH L A B C D

1 A

2 B

3 C

4 D

1 D

2 C

3 B

4 A

NOTE:

1. BE is selected at Master Reset; BM and SIZE must be static throughout device operation.

Figure 13. Port-B Byte Read Cycle Timing for FIFO1 (IDT Standard and FWFT Modes)

NOTE:

1. Read From FIFO2. Figure 14. Port-A Read Cycle Timing for FIFO2 (IDT Standard and FWFT Modes)

NOTE:

1. Unused bytes B9-B17, B18-B26, and B27-B35 are indeterminate.

EFB/ORB

MBB

CSB

W/RB

ENB

CLKB

HIGH

B0-B8

B0-B8 Read 5

Read 2 Read 3

Previous Data Read 2

No Operation

DIS

ENS2

ENH

(Standard Mode)

(FWFT Mode)

MDV

3270 drw15

3270 drw16

CLKA

EFA/ORA

ENA

MBA

CSA

W/RA

tCLK

tCLKH tCLKL

tMDV

tEN

tENH tENS2 tENH

W1 W2 W3

(1) (1)

tENH

tDIS

No Operation

A0-A35

(FWFT Mode)

tEN

(1) (1)

tDIS

Previous Data

A0-A35

(Standard Mode) tMDV tA

OR tA

tENS2

(1)

HIGH

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. tSKEW1 is the minimum time between a rising CLKA edge and a rising CLKB edge for ORB to transition HIGH and to clock the next word to the FIFO1 output register in three CLKB cycles.

If the time between the rising CLKA edge and rising CLKB edge is less than tSKEW1, then the transition of ORB HIGH and load of the first word to the output register may occur one CLKB

cycle later than shown.

2. If Port B size is word or byte, ORB is set LOW by the last word or byte read from FIFO1, respectively.

Figure 15. ORB Flag Timing and First Data Word Fall Through when FIFO1 is Empty (FWFT Mode)

CSA

WRA

MBA

IRA

A0-A35

CLKB

ORB

CSB

W/RB

MBB

ENA

ENB

B0-B35

CLKA

3270 drw17

123

tCLKH tCLKL

tCLK

tENS2 tENH

tENH

tDS tDH

tSKEW1 tCLKL

tREF tREF

tENS2 tENH

Old Data in FIFO1 Output Register W1

FIFO1 Empty

LOW

HIGH

LOW

HIGH

LOW

tCLKH

HIGH

(1)

tENS2

tCLK

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. tSKEW1 is the minimum time between a rising CLKA edge and a rising CLKB edge for EFB to transition HIGH in the next CLKB cycle. If the time between the rising CLKA edge

and rising CLKB edge is less than tSKEW1, then the transition of EFB HIGH may occur one CLKB cycle later than shown.

2. If Port B size is word or byte, EFB is set LOW by the last word or byte read from FIFO1, respectively.

Figure 16.

EFB

Flag Timing and First Data Read Fall Through when FIFO1 is Empty (IDT Standard Mode)

CSA

WRA

MBA

FFA

A0-A35

CLKB

EFB

CSB

W/RB

MBB

ENA

ENB

B0-B35

CLKA

3270 drw18

CLKH

CLKL

CLK

ENS2

ENH

SKEW1

CLK

CLKL

ENS2

ENH

FIFO1 Empty

LOW

HIGH

LOW

HIGH

LOW

CLKH

HIGH

(1)

REF

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. tSKEW1 is the minimum time between a rising CLKB edge and a rising CLKA edge for ORA to transition HIGH and to clock the next word to the FIFO2 output register in three CLKA cycles.

If the time between the CLKB edge and the rising CLKA edge is less than tSKEW1, then the transition of ORA HIGH and load of the first word to the output register may occur one CLKA

cycle later than shown.

2. If Port B size is word or byte, tSKEW1 is referenced to the rising CLKB edge that writes the last word or byte of the long word, respectively.

Figure 17. ORA Flag Timing and First Data Word Fall through when FIFO2 is Empty (FWFT Mode)

CSB

W/RB

MBB

IRB

B0-B35

CLKA

ORA

CSA

W/RA

MBA

ENB

ENA

A0-A35

CLKB

3270 drw19

123

tCLKH tCLKL

tCLK

tENS2

tENH

tDS tDH

tSKEW1(1) tCLK

tCLKH

tREF tREF

tENS2 tENH

Old Data in FIFO2 Output Register W1

FIFO2 Empty

tCLKL

LOW

HIGH

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. tSKEW1 is the minimum time between a rising CLKB edge and a rising CLKA edge for EFA to transition HIGH in the next CLKA cycle. If the time between the rising CLKB edge

and rising CLKA edge is less than tSKEW1, then the transition of EFA HIGH may occur one CLKA cycle later than shown.

2. If Port B size is word or byte, tSKEW1 is referenced to the rising CLKB edge that writes the last word or byte of the long word, respectively.

Figure 18.

EFA

Flag Timing and First Data Read when FIFO2 is Empty (IDT Standard Mode)

CSB

W/RB

MBB

FFB

B0-B35

CLKA

EFA

CSA

W/RA

MBA

ENB

ENA

A0-A35

CLKB

3270 drw20

CLKH

CLKL

CLK

ENS2

ENH

SKEW1

(1) t

CLK

CLKL

ENS2

ENH

FIFO2 Empty

LOW

CLKH

HIGH

REF

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 19. IRA Flag Timing and First Available Write when FIFO1 is Full (FWFT Mode)

NOTES:

1. tSKEW1 is the minimum time between a rising CLKB edge and a rising CLKA edge for IRA to transition HIGH in the next CLKA cycle. If the time between the rising CLKB edge and rising

CLKA edge is less than tSKEW1, then IRA may transition HIGH one CLKA cycle later than shown.

2. If Port B size is word or byte, tSKEW1 is referenced to the rising CLKB edge that reads the last word or byte write of the long word, respectively.

CSB

ORB

W/RB

MBB

ENB

B0-B35

CLKB

IRA

CLKA

CSA

3270 drw21

W/RA

A0-A35

MBA

ENA

tCLK

tCLKH tCLKL

tENS2 tENH

tSKEW1 tCLK

tCLKH tCLKL

tWFF

tENS2

tDS

tENH

tDH

To FIFO1

Previous Word in FIFO1 Output Register Next Word From FIFO1

LOW

HIGH

LOW

HIGH

LOW

HIGH

(1)

FIFO1 Full

tWFF

Write

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 20.

FFA

Flag Timing and First Available Write when FIFO1 is Full (IDT Standard Mode)

NOTES:

1. tSKEW1 is the minimum time between a rising CLKB edge and a rising CLKA edge for FFA to transition HIGH in the next CLKA cycle. If the time between the rising CLKB edge

and rising CLKA edge is less than tSKEW1, then FFA may transition HIGH one CLKA cycle later than shown.

2. If Port B size is word or byte, tSKEW1 is referenced from the rising CLKB edge that reads the last word or byte of the long word, respectively.

CSB

EFB

MBB

ENB

B0-B35

CLKB

FFA

CLKA

CSA

3270 drw22

W/RA

A0-A35

MBA

ENA

tCLK

tCLKH tCLKL

tENS2 tENH

tSKEW1 tCLK

tCLKH tCLKL

tENS2

tDS

tENH

tDH

To FIFO1

Previous Word in FIFO1 Output Register Next Word From FIFO1

LOW

W/RB HIGH

LOW

HIGH

LOW

HIGH

(1)

FIFO1 Full

tWFF tWFF

Write

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

NOTES:

1. tSKEW1 is the minimum time between a rising CLKA edge and a rising CLKB edge for IRB to transition HIGH in the next CLKB cycle. If the time between the rising CLKA edge and rising

CLKB edge is less than tSKEW1, then IRB may transition HIGH one CLKB cycle later than shown.

2. If Port B size is word or byte, IRB is set LOW by the last word or byte write of the long word, respectively.

Figure 21. IRB Flag Timing and First Available Write when FIFO2 is Full (FWFT Mode)

CSA

ORA

W/RA

MBA

ENA

A0-A35

CLKA

IRB

CLKB

CSB

3270 drw23

W/RB

B0-B35

MBB

ENB

tCLK

tCLKH tCLKL

tENS2 tENH

tSKEW1 tCLK

tCLKH tCLKL

tWFF tWFF

tENS2

tENH

tDS tDH

To FIFO2

Previous Word in FIFO2 Output Register Next Word From FIFO2

FIFO2 FULL

LOW

HIGH

LOW

(1)

Write

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 22.

FFB

Flag Timing and First Available Write when FIFO2 is Full (IDT Standard Mode)

NOTES:

1. tSKEW1 is the minimum time between a rising CLKA edge and a rising CLKB edge for FFB to transition HIGH in the next CLKB cycle. If the time between the rising CLKA edge

and rising CLKB edge is less than tSKEW1, then FFB may transition HIGH one CLKB cycle later than shown.

2. If Port B size is word or byte, FFB is set LOW by the last word or byte write of the long word, respectively.

tCLKH

CSA

EFA

MBA

ENA

A0-A35

CLKA

FFB

CLKB

CSB

3270 drw24

W/RB

B0-B35

MBB

ENB

tCLK

tCLKH tCLKL

tENS2 tENH

tSKEW1 tCLK tCLKL

tENS2

tDS

tENH

tDH

To FIFO2

Previous Word in FIFO2 Output Register Next Word From FIFO2

LOW

W/RALOW

LOW

HIGH

LOW

(1)

FIFO2 Full

tWFF tWFF

Write

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 25. Timing for

AFA

when FIFO1 is Almost-Full (IDT Standard and FWFT Modes)

Figure 23. Timing for

AEB

when FIFO1 is Almost-Empty (IDT Standard and FWFT Modes)

Figure 24. Timing for

AEA

when FIFO2 is Almost-Empty (IDT Standard and FWFT Modes)

NOTES:

1. tSKEW2 is the minimum time between a rising CLKA edge and a rising CLKB edge for AEB to transition HIGH in the next CLKB cycle. If the time between the rising CLKA edge

and rising CLKB edge is less than tSKEW2, then AEB may transition HIGH one CLKB cycle later than shown.

2 . FIFO1 Write (CSA = LOW, W/RA = LOW, MBA = LOW), FIFO1 read (CSB = LOW, W/RB = HIGH, MBB = LOW). Data in the FIFO1 output register has been read from the FIFO.

3. If Port B size is word or byte, AEB is set LOW by the last word or byte read from FIFO1, respectively.

NOTES:

1. tSKEW2 is the minimum time between a rising CLKB edge and a rising CLKA edge for AEA to transition HIGH in the next CLKA cycle. If the time between the rising CLKB edge

and rising CLKA edge is less than tSKEW2, then AEA may transition HIGH one CLKA cycle later than shown.

2 . FIFO2 Write (CSB = LOW, W/RB = LOW, MBB = LOW), FIFO2 read (CSA = LOW, W/RA = LOW, MBA = LOW). Data in the FIFO2 output register has been read from the FIFO.

3. If Port B size is word or byte, tSKEW2 is referenced to the rising CLKB edge that writes the last word or byte of the long word, respectively.

NOTES:

1. tSKEW2 is the minimum time between a rising CLKA edge and a rising CLKB edge for AFA to transition HIGH in the next CLKA cycle. If the time between the rising CLKA edge

and rising CLKB edge is less than tSKEW2, then AFA may transition HIGH one CLKA cycle later than shown.

2 . FIFO1 Write (CSA = LOW, W/RA = HIGH, MBA = LOW), FIFO1 read (CSB = LOW, W/RB = HIGH, MBB = LOW). Data in the FIFO1 output register has been read from the FIFO.

3. D = Maximum FIFO Depth = 256 for the IDT723624, 512 for the IDT723634, 1,024 for the IDT723644.

4. If Port B size is word or byte, tSKEW2 is referenced to the rising CLKB edge that reads the last word or byte of the long word, respectively.

AEB

CLKA

ENB

3270 drw25

ENA

CLKB 2

tENS2 tENH

tSKEW2

tPAE tPAE

tENS2 tENH

X1 Words in FIFO1 (X1+1) Words in FIFO1

(1)

AEA

CLKB

ENA

3270 drw26

ENB

CLKA 2

ENS2

ENH

SKEW2

PAE

ENS2

ENH

(X2+1) Words in FIFO2

X2 Words in FIFO2

(1)

AFA

CLKA

ENB

3270 drw 27

ENA

CLKB

tSKEW2

tENS2 tENH

tPAF

tENS2 tENH

tPAF

[D-(Y1+1)] Words in FIFO1 (D-Y1) Words in FIFO1

(1)

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 26. Timing for

AFB

when FIFO2 is Almost-Full (IDT Standard and FWFT Modes)

Figure 27. Timing for Mail1 Register and

MBF1

Flag (IDT Standard and FWFT Modes)

NOTE:

1. If Port B is configured for word size, data can be written to the Mail1 register using A0-A17 (A18-A35 are don't care inputs). In this first case B0-B17 will have valid data (B18-B35 will be

indeterminate). If Port B is configured for byte size, data can be written to the Mail1 Register using A0-A8 (A9-A35 are don't care inputs). In this second case, B0-B8 will have valid data

(B9-B35 will be indeterminate).

NOTES:

1. tSKEW2 is the minimum time between a rising CLKB edge and a rising CLKA edge for AFB to transition HIGH in the next CLKB cycle. If the time between the rising CLKB edge

and rising CLKA edge is less than tSKEW2, then AFB may transition HIGH one CLKB cycle later than shown.

2 . FIFO2 write (CSB = LOW, W/RB = LOW, MBB = LOW), FIFO2 read (CSA = LOW, W/RA = LOW, MBA = LOW). Data in the FIFO2 output register has been read from the FIFO.

3. D = Maximum FIFO Depth = 256 for the IDT723624, 512 for the IDT723634, 1,024 for the IDT723644.

4. If Port B size is word or byte, AFB is set LOW by the last word or byte write of the long word, respectively.

AFB

CLKB

ENA

3270 drw28

ENB

CLKA

SKEW2

ENH

PAF

ENS2

ENH

PAF

[D-(Y2+1)] Words in FIFO2 (D-Y2) Words in FIFO2

(1)

ENS2

3270 drw29

CLKA

ENA

A0-A35

MBA

CSA

W/RA

CLKB

MBF1

CSB

MBB

ENB

B0-B35

W/RB

ENS1

ENH

PMF

ENS2

ENH

DIS

MDV

PMR

FIFO1 Output Register

W1 (Remains valid in Mail1 Register after read)

ENH

ENS1

ENS2

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

Figure 28. Timing for Mail2 Register and

MBF2

Flag (IDT Standard and FWFT Modes)

NOTE:

1. If Port B is configured for word size, data can be written to the Mail2 Register using B0-B17 (B18-B35 are don’t care inputs). In this first case A0-A17 will have valid data

(A18-A35 will be indeterminate). If Port B is configured for byte size, data can be written to the Mail2 Register using B0-B8 (B9-B35 are don’t care inputs). In this second

case, A0-A8 will have valid data (A9-A35 will be indeterminate).

3270 drw30

CLKB

ENB

B0-B35

MBB

CSB

W/RB

CLKA

MBF2

CSA

MBA

ENA

A0-A35

W/RA

tENH

tDH

tPMF tPMF

tENS2 tENH

tDIS

tEN tMDV

tPMR

FIFO2 Output Register

W1 (Remains valid in Mail 2 Register after read)

tENH

tDS

tENS1

tENS2

COMMERCIAL TEMPERATURE RANGE

IDT723624/723634/723644 CMOS SyncBiFIFO™ WITH BUS-MATCHING

256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2

3270 drw31

PARAMETER MEASUREMENT INFORMATION

From Output

Under Test

30 pF

1.1 k Ω

5 V

680 Ω

PROPAGATION DELAY

LOAD CIRCUIT

3 V

GND

Timing

Input

Data,

Enable

Input

GND

3 V

1.5 V

VOLTAGE WAVEFORMS

SETUP AND HOLD TIMES VOLTAGE WAVEFORMS

PULSE DURATIONS

VOLTAGE WAVEFORMS

ENABLE AND DISABLE TIMES VOLTAGE WAVEFORMS

PROPAGATION DELAY TIMES

3 V

GND

3 V

1.5 V

Output

Enable

Low-Level

Output

High-Level

Output

3 V

GND

3 V

1.5 V 1.5 V

1.5 V

≈

GND

1.5 V 1.5 V

Input

In-Phase

Output

High-Level

Input

Low-Level

Input

1.5 V

3 V

PLZ

PHZ

PZL

PZH

(1)

Figure 29. Output Load and AC Test Conditions

NOTE:

1. Includes probe and jig capacitance.

CORPORATE HEADQUARTERS for SALES: for Tech Support:

6024 Silver Creek Valley Road 800-345-7015 or 408-284-8200 408-360-1753

San Jose, CA 95138 fax: 408-284-2775 em ail: FIFOhel p@idt.com

www.idt.com

3270 drw32

XXXXXX

IDT

Device Type

XXX X X

Power Speed Package Process/

Temperature

Range

Clock Cycle Time (t

CLK

)

Speed in Nanoseconds

Commercial Only

BLANK

723624

723634

723644

Commercial (0°C to +70°C)

Thin Quad Flat Pack (TQFP, PK128-1)

Low Power

256 x 36 x 2  SyncBiFIFO



with Bus-Matching

512 x 36 x 2  SyncBiFIFO



with Bus-Matching

1,024 x 36 x 2  SyncBiFIFO



with Bus-Matching

ORDERING INFORMATION

NOTE:

1. Industrial temperature range is available by special order.

DATASHEET DOCUMENT HISTORY

10/04/2000 pgs. 1 through 35, except pgs. 20, 24-26, 32 and 33.

03/22/2001 pgs. 6 and 7.

08/01/2001 pgs. 1, 6, 8, 9 and 35.