1Doc. No. MD-1004, Rev. E© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
FEATURES
■Fast read access times: 120/150ns
■Low power CMOS dissipation:
–Active: 25 mA max
–Standby: 150 µA max
■Simple write operation:
–On-chip address and data latches
–Self-timed write cycle with auto-clear
■Fast write cycle time:
–5ms max
■CMOS and TTL compatible I/O
■Hardware and software write protection
■Automatic page write operation:
–1 to 64 bytes in 5ms
–Page load timer
■End of write detection:
–Toggle bit
–DATADATA
DATADATA
DATA polling
■100,000 program/erase cycles
■100 year data retention
■Commerical, industrial and automotive
temperature ranges
DESCRIPTION
The CAT28C256 is a fast, low power, 5V-only CMOS
parallel EEPROM organized as 32K x 8-bits. It requires a
simple interface for in-system programming. On-chip
address and data latches, self-timed write cycle with auto-
clear and VCC power up/down write protection eliminate
additional timing and protection hardware. DATA Polling
and Toggle status bits signal the start and end of the self-
timed write cycle. Additionally, the CAT28C256 features
hardware and software write protection.
The CAT28C256 is manufactured using Catalyst’s ad-
vanced CMOS floating gate technology. It is designed to
endure 100,000 program/erase cycles and has a data
retention of 100 years. The device is available in JEDEC
approved 28-pin DIP, 28-pin TSOP or 32-pin PLCC
packages.
BLOCK DIAGRAM
ADDR. BUFFER
& LATCHES
ADDR. BUFFER
& LATCHES
INADVERTENT
WRITE
PROTECTION
CONTROL
LOGIC
TIMER
ROW
DECODER
COLUMN
DECODER
HIGH V OL TA GE
GENERATOR
A6–A14
CE
OE
WE
A0–A5
I/O0–I/O7
I/O BUFFERS
32,768 x 8
EEPROM
ARRAY
64 BYTE PAGE
REGISTER
VCC
DATA POLLING
AND
TOGGLE BIT
256K-Bit PARALLEL EEPROM
CAT28C256
CAT28C256
2
Doc. No. MD-1004, Rev. E © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
PIN CONFIGURATION
TSOP Package (8mm X 13.4mm) (T13, H13)
A13
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
I/O6
I/O5
I/O4
GND
I/O2
A1
A2
VCC
WE
A8
A9
A11
OE
A7
A6
A5
A4
A3
A10
I/O7
A12
16
15
CE
I/O3
I/O1
I/O0
A0
A14
PLCC Package (N, G)DIP Package (P, L)
I/O2
VSS
I/O6
I/O5
13
14
20
19
18
17
9
10
11
12
24
23
22
21
A1
A0
I/O0
I/O1
OE
A10
CE
I/O7
A5
A4
A3
A2
5
6
7
8
1
2
3
4
A14
A12
A7
A6A9
A11
28
27
26
25
VCC
WE
A13
A8A6
A5
A4
A3
5
6
7
8
A2
A1
A0
NC
9
10
11
12
I/O013
A8
A9
A11
NC
29
28
27
26 OE
A10
CE
25
24
23
22 I/O7
21
I/O1
I/O2
V
SS
NC
I/O3
I/O4
I/O5
14 15 16 17 18 19 20
4321323130
A7
A12
A14
NC
VCC
WE
A13
I/O4
I/O3
16
15
I/O6
TOP VIEW
PIN FUNCTIONS
Pin Name Function
A0–A14 Address Inputs
I/O0–I/O7Data Inputs/Outputs
CE Chip Enable
OE Output Enable
Pin Name Function
WE Write Enable
VCC 5V Supply
VSS Ground
NC No Connect
CAT28C256
3Doc. No. MD-1004, Rev. E© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
D.C. OPERATING CHARACTERISTICS
VCC = 5V ±10%, unless otherwise specified.
Limits
Symbol Parameter Min. Typ. Max. Units Test Conditions
ICC VCC Current (Operating, TTL) 30 mA CE = OE = VIL, f=8MHz
All I/O’s Open
ICCC(5) VCC Current (Operating, CMOS) 25 mA CE = OE = VILC, f=8MHz
All I/O’s Open
ISB VCC Current (Standby, TTL) 1 mA CE = VIH, All I/O’s Open
ISBC(6) VCC Current (Standby, CMOS) 150 µA CE = VIHC,
All I/O’s Open
ILI Input Leakage Current –10 10 µAV
IN = GND to VCC
ILO Output Leakage Current –10 10 µAV
OUT = GND to VCC,
CE = VIH
VIH(6) High Level Input Voltage 2 VCC +0.3 V
VIL(5) Low Level Input Voltage –0.3 0.8 V
VOH High Level Output Voltage 2.4 V IOH = –400µA
VOL Low Level Output Voltage 0.4 V IOL = 2.1mA
VWI Write Inhibit Voltage 3.5 V
*COMMENT
Stresses above 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 outside of
those listed in the operational sections of this specifica-
tion is not implied. Exposure to any absolute maximum
rating for extended periods may affect device perfor-
mance and reliability.
ABSOLUTE MAXIMUM RATINGS*
Temperature Under Bias ................. –55°C to +125°C
Storage Temperature....................... –65°C to +150°C
Voltage on Any Pin with
Respect to Ground(2) ........... –2.0V to +VCC + 2.0V
VCC with Respect to Ground ............... –2.0V to +7.0V
Package Power Dissipation
Capability (Ta = 25°C)................................... 1.0W
Lead Soldering Temperature (10 secs)............ 300°C
Output Short Circuit Current(3) ........................ 100 mA
RELIABILITY CHARACTERISTICS
Symbol Parameter Min. Max. Units Test Method
NEND(1) Endurance 100,000 Cycles/Byte MIL-STD-883, Test Method 1033
TDR(1) Data Retention 100 Years MIL-STD-883, Test Method 1008
VZAP(1) ESD Susceptibility 2000 Volts MIL-STD-883, Test Method 3015
ILTH(1)(4) Latch-Up 100 mA JEDEC Standard 17
Note:
(1) This parameter is tested initially and after a design or process change that affects the parameter.
(2) The minimum DC input voltage is –0.5V. During transitions, inputs may undershoot to –2.0V for periods of less than 20 ns. Maximum DC
voltage on output pins is VCC +0.5V, which may overshoot to VCC +2.0V for periods of less than 20 ns.
(3) Output shorted for no more than one second. No more than one output shorted at a time.
(4) Latch-up protection is provided for stresses up to 100mA on address and data pins from –1V to VCC +1V.
(5) VILC = –0.3V to +0.3V.
(6) VIHC = VCC –0.3V to VCC +0.3V.
CAT28C256
4
Doc. No. MD-1004, Rev. E © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
28C256-12 28C256-15
Symbol Parameter Min. Max. Min. Max. Units
tRC Read Cycle Time 120 150 ns
tCE CE Access Time 120 150 ns
tAA Address Access Time 120 150 ns
tOE OE Access Time 50 70 ns
tLZ(1) CE Low to Active Output 0 0 ns
tOLZ(1) OE Low to Active Output 0 0 ns
tHZ(1)(2) CE High to High-Z Output 50 50 ns
tOHZ(1)(2) OE High to High-Z Output 50 50 ns
tOH(1) Output Hold from Address Change 0 0 ns
MODE SELECTION
Mode CE WE OE I/O Power
Read L H L DOUT ACTIVE
Byte Write (WE Controlled) L H DIN ACTIVE
Byte Write (CE Controlled) L H DIN ACTIVE
Standby, and Write Inhibit H X X High-Z STANDBY
Read and Write Inhibit X H H High-Z ACTIVE
CAPACITANCE TA = 25°C, f = 1.0 MHz, VCC = 5V
Symbol Test Max. Units Conditions
CI/O(1) Input/Output Capacitance 10 pF VI/O = 0V
CIN(1) Input Capacitance 6 pF VIN = 0V
Note:
(1) This parameter is tested initially and after a design or process change that affects the parameter.
(2) Output floating (High-Z) is defined as the state when the external data line is no longer driven by the output buffer.
A.C. CHARACTERISTICS, Read Cycle
VCC=5V + 10%, Unless otherwise specified
CAT28C256
5Doc. No. MD-1004, Rev. E© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
Note:
(1) This parameter is tested initially and after a design or process change that affects the parameter.
(2) Input rise and fall times (10% and 90%) < 10 ns.
(3) A write pulse of less than 20ns duration will not initiate a write cycle.
(4) A timer of duration tBLC max. begins with every LOW to HIGH transition of WE. If allowed to time out, a page or byte write will begin;
however a transition from HIGH to LOW within tBLC max. stops the timer.
Figure 1. A.C. Testing Input/Output Waveform(2)
1.3V
DEVICE
UNDER
TEST
1N914
3.3K
CL = 100 pF
OUT
CL INCLUDES JIG CAPACITANCE
Figure 2. A.C. Testing Load Circuit (example)
A.C. CHARACTERISTICS, Write Cycle
VCC=5V+10%, unless otherwise specified
28C256-12 28C256-15
Symbol Parameter Min. Max. Min. Max. Units
tWC Write Cycle Time 5 5 ms
tAS Address Setup Time 0 0 ns
tAH Address Hold Time 50 50 ns
tCS CE Setup Time 0 0 ns
tCH CE Hold Time 0 0 ns
tCW(3) CE Pulse Time 100 100 ns
tOES OE Setup Time 0 0 ns
tOEH OE Hold Time 0 0 ns
tWP(3) WE Pulse Width 100 100 ns
tDS Data Setup Time 50 50 ns
tDH Data Hold Time 10 10 ns
tINIT(1) Write Inhibit Period After Power-up 5 10 5 10 ms
tBLC(1)(4) Byte Load Cycle Time 0.1 100 0.1 100 µs
INPUT PULSE LEVELS REFERENCE POINTS
2.0 V
0.8 V
VCC - 0.3V
0.0 V
CAT28C256
6
Doc. No. MD-1004, Rev. E © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
ADDRESS
CE
OE
WE
tRC
DATA OUT D A TA VALIDD A TA VALID
tCE
tOE
tOH
tAA
tOHZ
tHZ
VIH
HIGH-Z
tLZ
tOLZ
DEVICE OPERATION
Read
Data stored in the CAT28C256 is transferred to the data
bus when WE is held high, and both OE and CE are
held low. The data bus is set to a high impedance state
when either CE or OE goes high. This 2-line control
architecture can be used to eliminate bus contention in
a system environment.
Byte Write
A write cycle is executed when both CE and W E are low,
and OE is high. Write cycles can be initiated using either
WE or CE, with the address input being latched on the
falling edge of WE or CE, whichever occurs last. Data,
conversely, is latched on the rising edge of WE or CE,
whichever occurs first. Once initiated, a byte write cycle
automatically erases the addressed byte and the new
data is written within 5 ms.
Figure 3. Read Cycle
Figure 4. Byte Write Cycle [WE Controlled]
ADDRESS
CE
OE
WE
DATA OUT
tAS
DATA IN D A TA VALID
HIGH-Z
tCS
tAH tCH
tWC
tOEH
tBLC
tDH
tDS
tOES tWP
CAT28C256
7Doc. No. MD-1004, Rev. E© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
Page Write
The page write mode of the CAT28C256 (essentially an
extended BYTE WRITE mode) allows from 1 to 64 bytes
of data to be programmed within a single EEPROM write
cycle. This effectively reduces the byte-write time by a
factor of 64.
Following an initial WRITE operation (WE pulsed low, for
tWP, and then high) the page write mode can begin by
issuing sequential WE pulses, which load the address
and data bytes into a 64 byte temporary buffer. The page
address where data is to be written, specified by bits A6
to A14, is latched on the last falling edge of WE. Each
byte within the page is defined by address bits A0 to A5
(which can be loaded in any order) during the first and
subsequent write cycles. Each successive byte load
cycle must begin within tBLC MAX of the rising edge of the
preceding WE pulse. There is no page write window
limitation as long as WE is pulsed low within tBLC MAX.
Upon completion of the page write sequence, WE must
stay high a minimum of tBLC MAX for the internal auto-
matic program cycle to commence. This programming
cycle consists of an erase cycle, which erases any data
that existed in each addressed cell, and a write cycle,
which writes new data back into the cell. A page write will
only write data to the locations that were addressed and
will not rewrite the entire page.
Figure 5. Byte Write Cycle [CE Controlled]
Figure 6. Page Mode Write Cycle
OE
CE
WE
ADDRESS
I/O
tWP tBLC
BYTE 0 BYTE 1 BYTE 2 BYTE n BYTE n+1 BYTE n+2
LAST BYTE
tWC
ADDRESS
CE
OE
WE
DATA OUT
tAS
DATA IN D A TA VALID
HIGH-Z
tAH
tWC
tOEH
tDH
tDS
tOES
tBLC
tCH
tCS
tCW
CAT28C256
8
Doc. No. MD-1004, Rev. E © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
WE
CE
OE
I/O6
tOEH tOE tOES
tWC
(1) (1)
ADDRESS
CE
WE
OE
I/O7DIN = X DOUT = X DOUT = X
tOE
tOEH
tWC
tOES
DATA Polling
DATA polling is provided to indicate the completion of
write cycle. Once a byte write or page write cycle is
initiated, attempting to read the last byte written will
output the complement of that data on I/O7 (I/O0–I/O6
are indeterminate) until the programming cycle is com-
plete. Upon completion of the self-timed write cycle, all
I/O’s will output true data during a read cycle.
Toggle Bit
In addition to the DATA Polling feature of the CAT28C256,
the device offers an additional method for determining
the completion of a write cycle. While a write cycle is in
progress, reading data from the device will result in I/O6
toggling between one and zero. However, once the write
is complete, I/O6 stops toggling and valid data can be
read from the device.
Figure 7. DATA Polling
Figure 8. Toggle Bit
Note:
(1) Beginning and ending state of I/O6 is indeterminate.
CAT28C256
9Doc. No. MD-1004, Rev. E© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
Note:
(1) Write protection is activated at this point whether or not any more writes are completed. Writing to addresses must occur within tBLC
Max., after SDP activation.
HARDWARE DATA PROTECTION
The following is a list of hardware data protection fea-
tures that are incorporated into the CAT28C256.
(1) VCC sense provides for write protection when VCC
falls below 3.5V min.
(2) A power on delay mechanism, tINIT (see AC charac-
teristics), provides a 5 to 10 ms delay before a write
sequence, after VCC has reached 3.5V min.
(3) Write inhibit is activated by holding any one of OE
low, CE high or WE high.
(4) Noise pulses of less than 20 ns on the WE or CE
inputs will not result in a write cycle.
SOFTWARE DATA PROTECTION
The CAT28C256 features a software controlled data
protection scheme which, once enabled, requires a data
algorithm to be issued to the device before a write can be
performed. The device is shipped from Catalyst with the
software protection NOT ENABLED (the CAT28C256 is
in the standard operating mode).
Figure 9. Write Sequence for Activating Software
Data Protection Figure 10. Write Sequence for Deactivating
Software Data Protection
WRITE DATA: AA
ADDRESS: 5555
WRITE DATA: 55
ADDRESS: 2AAA
WRITE DATA: 80
ADDRESS: 5555
WRITE DATA: AA
ADDRESS: 5555
WRITE DATA: 55
ADDRESS: 2AAA
WRITE DATA: 20
ADDRESS: 5555
SOFTWARE DATA
PRO TECTION A CTIV A TED (12)
WRITE DATA: XX
WRITE LAST BYTE
TO
LAST ADDRESS
TO ANY ADDRESS
WRITE DATA: AA
ADDRESS: 5555
WRITE DATA: 55
ADDRESS: 2AAA
WRITE DATA: A0
ADDRESS: 5555
(1)
CAT28C256
10
Doc. No. MD-1004, Rev. E © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
To activate the software data protection, the device must
be sent three write commands to specific addresses with
specific data (Figure 9). This sequence of commands
(along with subsequent writes) must adhere to the page
write timing specifications (Figure 11). Once this is done,
all subsequent byte or page writes to the device must be
preceded by this same set of write commands. The data
protection mechanism is activated until a deactivate
sequence is issued regardless of power on/off transi-
tions. This gives the user added inadvertent write pro-
tection on power-up in addition to the hardware protec-
tion provided.
To allow the user the ability to program the device with
an EEPROM programmer (or for testing purposes) there
is a software command sequence for deactivating the
data protection. The six step algorithm (Figure 10) will
reset the internal protection circuitry, and the device will
return to standard operating mode (Figure 12 provides
reset timing). After the sixth byte of this reset sequence
has been issued, standard byte or page writing can
commence.
Figure 11. Software Data Protection Timing
CE
WE
tWP
AA
5555 55
2AAA A0
5555
DATA
ADDRESS
tBLC
tWC
BYTE OR
PAGE
WRITES
ENABLED
Figure 12. Resetting Software Data Protection Timing
CE
WE
AA
5555 55
2AAA
DATA
ADDRESS tWC
80
5555 AA
5555 55
2AAA 20
5555 SDP
RESET
DEVICE
UNPROTECTED
CAT28C256
11 Doc. No. MD-1004, Rev. E© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
ORDERING INFORMATION
Notes:
(1) The device used in the above example is a CAT28C256NI-15T (PLCC, Industrial temperature, 150ns Access Time, Tape & Reel).
Speed
12: 120ns
15: 150ns
Prefix Device # Suffix
28C256
Product
Number
CAT
Optional
Company
ID
NI T
Tape & Reel
Package
P: PDIP
N: PLCC
T13: TSOP (8mmx13.4mm)
-15
Temperature Range
Blank = Commercial (0°C to +70°C)
I = Industrial (-40°C to +85°C)
A = Automotive (-40°C to +105°C)*
* -40°C to +125°C is available upon request
L: PDIP (Lead free, Halogen free)
G: PLCC (Lead free, Halogen free)
H13: TSOP (8mmx13.4mm) (Lead free, Halogen free)
CAT28C256
12
Doc. No. MD-1004, Rev. E © 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice
REVISION HISTORY
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