X25040
PIN DESCRIPTIONS
Serial Output (SO)
Hold (HOLD)
HOLD is used in conjunction with the CS pin to select the
device.Oncethepartisselectedandaserialsequenceis
underway, HOLD may be used to pause the serial
communication with the controller without resetting the
serialsequence. Topause, HOLDmustbebroughtLOW
while SCK is LOW. To resume communication, HOLD is
brought HIGH, again while SCK is LOW. If the pause
feature is not used, HOLD should be held HIGH at all
times.
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 ad-
dresses, and data to be written to the memory are input
onthispin. Dataislatchedbytherisingedgeoftheserial
clock.
PIN CONFIGURATION
Serial Clock (SCK)
DIP/SOIC
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.
CS
SO
WP
1
2
3
4
8
7
6
5
V
CC
HOLD
SCK
SI
X25040
V
SS
Chip Select (CS)
WhenCSisHIGH, theX25040isdeselectedandtheSO
output pin is at high impedance and unless an internal
write operation is underway, the X25040 will be in the
standby power mode. CS LOW enables the X25040,
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.
6451 FHD F02.1
PIN NAMES
Symbol
CS
SO
Description
Chip Select Input
Serial Output
Serial Input
Write Protect (WP)
SI
When WP is LOW, nonvolatile writes to the X25040 are
disabled, but the part otherwise functions normally.
WhenWPisheldHIGH, allfunctions, includingnonvola-
tile writes operate normally. WP going LOW while CS is
still LOW will interrupt a write to the X25040. If the
internal write cycle has already been initiated, WP going
LOW will have no affect on a write.
SCK
WP
VSS
Serial Clock Input
Write Protect Input
Ground
VCC
HOLD
Supply Voltage
Hold Input
6451 PGM T01
2
ICMIC [ IC MICROSYSTEMS ]
