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)
It should be noted that after power-up, a HIGH to LOW
transition on CS is required prior to the start of any
When CS is HIGH, the X25170 is deselected and the
SO output pin is at high impedance; unless an internal
write operation is underway, the X25170 will be in the
standby power mode. CS LOW enables the X25170,
placing it in the active power mode.
Write Protect (WP)
When WP is LOW and the nonvolatile bit WPEN is “1”,
nonvolatile writes to the X25170 status register are dis-
abled, 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 X25170 status reg-
ister. If the internal write cycle has already been initi-
ated, WP going LOW will have no effect 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 X25170 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”.
Chip Select Input
Serial Clock Input
Write Protect Input
WP 3 X25170 6 SCK
NC 4 X25170 11
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 com-
munication, HOLD is brought HIGH, again while SCK
is LOW. If the pause feature is not used, HOLD should
be held HIGH at all times.
Characteristics subject to change without notice. 2 of 15
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