X28C256
256K
X28C256
5 Volt, Byte Alterable E
2
PROM
32K x 8 Bit
FEATURES
DESCRIPTION
The X28C256 is an 32K x 8 E
2
PROM, fabricated with
Xicor’s proprietary, high performance, floating gate
CMOS technology. Like all Xicor programmable non-
volatile memories the X28C256 is a 5V only device. The
X28C256 features the JEDEC approved pinout for byte-
wide memories, compatible with industry standard RAMs.
The X28C256 supports a 64-byte page write operation,
effectively providing a 78µs/byte write cycle and en-
abling the entire memory to be typically written in less
than 2.5 seconds. The X28C256 also features
DATA
and Toggle Bit Polling, a system software support
scheme used to indicate the early completion of a write
cycle. In addition, the X28C256 includes a user-optional
software data protection mode that further enhances
Xicor’s hardware write protect capability.
Xicor E
2
PROMs are designed and tested for applica-
tions requiring extended endurance. Inherent data re-
tention is greater than 100 years.
•
•
•
•
•
•
•
Access Time: 200ns
Simple Byte and Page Write
— Single 5V Supply
—No External High Voltages or V
PP
Control
Circuits
— Self-Timed
—No Erase Before Write
—No Complex Programming Algorithms
—No Overerase Problem
Low Power CMOS:
—Active: 60mA
—Standby: 200
µ
A
Software Data Protection
— Protects Data Against System Level
Inadvertent Writes
High Speed Page Write Capability
Highly Reliable Direct Write
™
Cell
— Endurance: 100,000 Write Cycles
— Data Retention: 100 Years
Early End of Write Detection
—
DATA
Polling
—Toggle Bit Polling
PIN CONFIGURATION
VCC
A12
A14
A13
WE
NC
A7
PLASTIC DIP
CERDIP
FLAT PACK
SOIC
A14
A12
A7
A6
A5
A4
A3
A2
A1
A0
I/O0
I/O1
I/O2
VSS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
X28C256
28
27
26
25
24
23
22
21
20
19
18
17
16
15
VCC
WE
A13
A8
A9
A11
OE
A10
CE
I/O7
I/O6
I/O5
I/04
I/O3
LCC
PLCC
TSOP
A2
A1
A0
I/O0
I/O1
I/O2
NC
VSS
NC
I/O3
I/O4
I/O5
I/O6
I/O7
CE
A10
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
A3
A4
A5
A6
A7
A12
A14
NC
VCC
NC
WE
A13
A8
A9
A11
OE
4
A6
A5
A4
A3
A2
A1
A0
NC
I/O0
5
6
7
8
9
10
11
12
3
2
1 32 31 30
29
28
27
26
A8
A9
A11
NC
OE
A10
CE
I/O7
I/O6
X28C256
X28C256
25
24
23
22
13
21
14 15 16 17 18 19 20
I/O1
I/O2
VSS
NC
I/O3
I/O4
I/O5
3855 ILL F23
3855 FHD F03
3855 FHD F02
© Xicor, Inc. 1991, 1995 Patents Pending
3855-1.9 8/1/97 T1/C0/D8 EW
1
Characteristics subject to change without notice