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Xicor

X25401 Datasheet Preview

X25401 Datasheet

SPI Serial AUTOSTORE NOVRAM

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APPLICATION NOTE
AVA I L A B L E
X25401
AN56
256 Bit
X25401
SPI Serial AUTOSTORE™ NOVRAM
16 x 16 Bit
FEATURES
1MHz Clock Rate
AUTOSTORE™ NOVRAM
—Automatically Performs a Store Operation
Upon Loss of VCC
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: 50µA
8-Lead PDIP and 8-Lead SOIC Packages
High Reliability
—Store Cycles: 1,000,000
—Data Retention: 100 Years
FUNCTIONAL DIAGRAM
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 E2PROM 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 E2PROM) is completed in 5ms or less
and a recall operation (E2PROM 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 VCC falls below a preset threshold.
Xicor NOVRAMs are designed for unlimited write opera-
tions to RAM, either from the host or recalls from E2PROM
and a minimum 1,000,000 store operations. Inherent data
retention is specified to be greater than 100 years.
NONVOLATILE
E2PROM
ROW
DECODE
STATIC
RAM
256-BIT
CONTROL
LOGIC
RECALL (6)
AS (7)
CS (1)
SI (3)
SCK (2)
INSTRUCTION
REGISTER
INSTRUCTION
DECODE
COLUMN
DECODE
4-BIT
COUNTER
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
SO (4)
2051 FHD F01
Characteristics subject to change without notice




Xicor

X25401 Datasheet Preview

X25401 Datasheet

SPI Serial AUTOSTORE NOVRAM

No Preview Available !

X25401
PIN DESCRIPTIONS
Chip Select (CS)
The Chip Select input must be LOW to enable all read/
write operations. CS must remain LOW following a
Read or Write command until the data transfer is com-
plete. CS HIGH places the X25401 in the low power
standby mode and resets the instruction register. There-
fore, CS must be brought HIGH after the completion of
an operation in order to reset the instruction register in
preparation for the next command.
Serial Clock (SCK)
The Serial Clock input is used to clock all data into and
out of the device.
Serial Data In (SI)
SI is the serial data input.
Serial Data Out (SO)
SO is the serial data output. It is in the high impedance
state except during data output cycles in response to a
READ instruction.
AUTOSTORE Output (AS)
AS is an open drain output which, when asserted indi-
cates VCC has fallen below the AUTOSTORE thresh-
old (VASTH). AS may be wire-ORed with multiple open
drain outputs and used as an interrupt input to a micro-
controller or as an input to a low power reset circuit.
RECALL
RECALL LOW will initiate an internal transfer of data
from E2PROM to the RAM array.
PIN CONFIGURATION
CS
SCK
SI
SO
DIP/SOIC
18
27
X25401
36
45
VCC
AS
RECALL
VSS
2051 FHD F02
PIN NAMES
Symbol
CS
SCK
SI
SO
RECALL
AS
VCC
VSS
Description
Chip Enable
Serial Clock
Serial Data In
Serial Data Out
Recall Input
AUTOSTORE Output
+5V
Ground
2051 PGM T01
2



Part Number X25401
Description SPI Serial AUTOSTORE NOVRAM
Maker Xicor
Total Page 14 Pages
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