A
PPLICATION
N
OTE
A V A I L A B L E
X25401
256 Bit
AN56
X25401
SPI Serial AUTOSTORE™ NOVRAM
16 x 16 Bit
FEATURES
DESCRIPTION
The Xicor X25401 is a serial 256 bit NOVRAM featuring
a static RAM configured 16 x 16, overlaid bit-by-bit with
a nonvolatile E
2
PROM array. The X25401 features a
Serial Peripheral Interface (SPI) and software protocol
allowing operation on a simple three-wire bus. The bus
signals are a clock input (SCK) plus separate data in (SI)
and data out (SO) lines. Access to the device is con-
trolled through a chip select (CS) input, allowing any
number of devices to share the same bus.
The Xicor NOVRAM design allows data to be transferred
between the two memory arrays by means of software
commands or external hardware inputs. A store opera-
tion (RAM data to E
2
PROM) is completed in 5ms or less
and a recall operation (E
2
PROM data to RAM) is com-
pleted in 2µs or less.
The X25401 also includes the AUTOSTORE feature, a
user selectable feature that automatically performs a
store operation when V
CC
falls below a preset threshold.
Xicor NOVRAMs are designed for unlimited write opera-
tions to RAM, either from the host or recalls from E
2
PROM
and a minimum 1,000,000 store operations. Inherent data
retention is specified to be greater than 100 years.
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1MHz Clock Rate
AUTOSTORE™ NOVRAM
—Automatically Performs a Store Operation
Upon Loss of V
CC
Single 5 Volt Supply
Ideal for use with Single Chip Microcomputers
—Minimum I/O Interface
—SPI Mode (0,0 & 1,1) Serial Port Compatible
—Easily Interfaced to Microcontroller Ports
Software and Hardware Control of Nonvolatile
Functions
Auto Recall on Power-Up
TTL and CMOS Compatible
Low Power Dissipation
—Active Current: 10mA
—Standby Current: 50
µ
A
8-Lead PDIP and 8-Lead SOIC Packages
High Reliability
—Store Cycles: 1,000,000
—Data Retention: 100 Years
FUNCTIONAL DIAGRAM
NONVOLATILE
2
E PROM
R
E
ROW
DECODE
STATIC
RAM
256-BIT
EC
AL
L
ST
O
CONTROL
LOGIC
R
RECALL (6)
AS (7)
CS (1)
SI (3)
SCK (2)
INSTRUCTION
REGISTER
COLUMN
DECODE
SO (4)
INSTRUCTION
DECODE
4-BIT
COUNTER
2051 FHD F01
AUTOSTORE™ NOVRAM is a trademark of Xicor, Inc.
COPS is a trademark of National Semiconductor Corp.
© Xicor, Inc. 1992, 1995, 1996 Patents Pending
2051-1.5 8/1/97 T0/C0/D2 SH
1
Characteristics subject to change without notice
XICOR [ XICOR INC. ]
