X25020
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 ad-
dresses, 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 X25020 is deselected and the SO
output pin is at high impedance and unless an internal
write operation is underway, the X25020 will be in the
standby power mode.
CS
LOW enables the X25020,
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, nonvolatile writes to the X25020 are
disabled, but the part otherwise functions normally.
When
WP
is held HIGH, all functions, including nonvola-
tile writes operate normally.
WP
going LOW while
CS
is
still LOW will interrupt a write to the X25020. If the
internal write cycle has already been initiated,
WP
going
LOW will have no affect on a write.
DIP/SOIC
Hold (HOLD)
HOLD
is used in conjunction with the
CS
pin to select the
device. Once the part is selected and a serial sequence is
underway,
HOLD
may be used to pause the serial
communication with the controller without resetting the
serial sequence. To pause,
HOLD
must be brought LOW
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.
PIN CONFIGURATION
CS
SO
WP
VSS
1
2
3
4
X25020
8
7
6
5
VCC
HOLD
SCK
SI
3834 FHD F02.1
PIN NAMES
Symbol
CS
SO
SI
SCK
WP
V
SS
V
CC
HOLD
Description
Chip Select Input
Serial Output
Serial Input
Serial Clock Input
Write Protect Input
Ground
Supply Voltage
Hold Input
3834 PGM T01.1
2
ICMIC [ IC MICROSYSTEMS ]
