FM25C160
Rev. 2.1
Aug. 2003
Page 2 of 14
Instruction Decode
Clock Generator
Control Logic
Write Protect
Instruction Register
Address Register
Counter
512 x 32
FRAM Array
11
Data I/O Register
8
Nonvolatile Status
Register
3
WP
CS
HOLD
SCK
SO
SI
Figure 1. Block Diagram
Pin Description
Pin Name
I/O
Pin Description
/CS
Input
Chip Select: This active low input activates the device. When high, the device enters
low-power standby mode, ignores other inputs, and all outputs are tri-stated. When
low, the device internally activates the SCK signal. A falling edge on /CS must occur
prior to every op-code.
SCK
Input
Serial Clock: All I/O activity is synchronized to the serial clock. Inputs are latched on
the rising edge and outputs occur on the falling edge. Since the device is static, the
clock frequency may be any value between 0 and 5 MHz and may be interrupted at
any time.
/HOLD
Input
Hold: The /HOLD pin is used when the host CPU must interrupt a memory operation
for another task. When /HOLD is low, the current operation is suspended. The device
ignores any transition on SCK or /CS. All transitions on /HOLD must occur while
SCK is low.
/WP
Input
Write Protect: This active low pin prevents write operations to the status register. This
is critical since other write protection features are controlled through the status
register. A complete explanation of write protection is provided on page 6. *Note that
the function of /WP is different from the FM25160.
SI
Input
Serial Input: All data is input to the device on this pin. The pin is sampled on the rising
edge of SCK and is ignored at other times. It should always be driven to a valid logic
level to meet IDD specifications.
* SI may be connected to SO for a single pin data interface.
SO
Output
Serial Output. SO is the data output pin. It is driven actively during a read and remains
tri-state at all other times including when /HOLD is low. Data transitions are driven on
the falling edge of the serial clock.
* SO may be connected to SI for a single pin data interface.
VDD
Supply
Supply Voltage. 5V
VSS
Supply
Ground
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