FM25V02 - 256Kb SPI FRAM
W
S
Instruction Decode
Clock Generator
Control Logic
HOLD
C
Write Protect
4096 x 64
FRAM Array
Instruction Register
15
8
Address Register
Counter
Q
D
Data I/O Register
3
Nonvolatile Status
Register
Figure 1. Block Diagram
Pin Descriptions
Pin Name
I/O
Description
/S
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 C signal. A falling edge on /S must occur prior
to every op-code.
C
Input
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 40 MHz and may be interrupted at
any time.
/HOLD
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 C or /S. All transitions on /HOLD must occur while C is low.
This pin has a weak internal pull-up (see RIN spec, pg 11). However, if it is not used,
the /HOLD pin should be tied to VDD
.
/W
D
Input
Input
Write Protect: This active-low pin prevents write operations to the Status Register
only. A complete explanation of write protection is provided on pages 6 and 7. If not
used, the /W pin should be tied to VDD
.
Serial Input: All data is input to the device on this pin. The pin is sampled on the
rising edge of C and is ignored at other times. It should always be driven to a valid
logic level to meet IDD specifications.
* D may be connected to Q for a single pin data interface.
Serial Output: This is the data output pin. It is driven during a read and remains tri-
stated at all other times including when /HOLD is low. Data transitions are driven on
the falling edge of the serial clock.
Q
Output
* Q may be connected to D for a single pin data interface.
Power Supply
Ground
VDD
VSS
Supply
Supply
Rev. 2.0
May 2010
Page 2 of 17
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
