X25138 datasheet(2/18 Pages) XICOR

2 / 18 page

X25138

PIN DESCRIPTIONS

Serial Output (SO)

SO is a push/pull serial data output pin. During a read

cycle, data is shifted out on this pin. Data is clocked

out by the falling edge of the serial clock.

Serial Input (SI)

SI is the serial data input pin. All opcodes, byte

addresses, and data to be written to the memory are

input on this pin. Data is latched by the rising edge of

the serial clock.

Serial Clock (SCK)

The Serial Clock controls the serial bus timing for data

input and output. Opcodes, addresses, or data present

on the SI pin are latched on the rising edge of the

clock input, while data on the SO pin change after the

falling edge of the clock input.

Chip Select (CS)

When CS is HIGH, the X25138 is deselected and the

SO output pin is at high impedance and unless an

internal write operation is underway, the X25138 will be

in the standby power mode. CS LOW enables the

X25138, placing it in the active power mode. It should

be noted that after power-up, a HIGH to LOW transition

on CS is required prior to the start of any operation.

Write Protect (WP)

When WP is LOW and the nonvolatile bit WPEN is “1”,

nonvolatile writes to the X25138 status register are

disabled, but the part otherwise functions normally.

When WP is held HIGH, all functions, including

nonvolatile writes operate normally. WP going LOW

while CS is still LOW will interrupt a write to the

X25138 status register. If the internal write cycle has

already been initiated, WP going LOW will have no

affect on a write.

The WP pin function is blocked when the WPEN bit in

the status register is “0”. This allows the user to install

the X25138 in a system with WP pin grounded and still

be able to write to the status register. The WP pin func-

tions will be enabled when the WPEN bit is set “1”.

Hold (HOLD)

HOLD is used in conjunction with the CS pin to pause

the device. Once the part is selected and a serial

sequence is underway, HOLD may be used to pause

14 Lead SOIC

X25138

VSS

.228”

.336”

8 Lead PDIP/SOIC

VCC

HOLD

SCK

X25138

VSS

VCC

HOLD

SCK

8-Lead XBGA: Top View

SCK

VCC

VSS

HOLD

.238”

SCK

8-LEAD TSSOP

X25138

.252 in.

Vss

HOLD

.078”

Vcc

3091 FM 03

.114”

PIN NAMES

7037 FRM T01

Symbol

Description

Chip Select Input

Serial Output

Serial Input

SCK

Serial Clock Input

Write Protect Input

VSS

Ground

VCC

Supply Voltage

HOLD

Hold Input

No Connect

PIN CONFIGURATION

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