FM25L256 Extended Temp.
WP
CS
Instruction Decode
Clock Generator
Control Logic
HOLD
SCK
Write Protect
8192 x 32
FRAM Array
Instruction Register
15
8
Address Register
Counter
SI
SO
Data I/O Register
3
D
E
Nonvolatile Status
Register
D
Figure 1. Block Diagram
S
N
ME
N
Pin Descriptions
G
Pin Name
/CS
I/O
Input
Description
I
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-stBated. When
S
6
low, the device internally activMates the SCK signal. A falling edge on /CS must occur
5
prior to every op-code.
Serial Clock: All I/O ac
E
tivity is synchronized to the serial clock.2Inputs are latched on
SCK
Input
Input
O
the rising edge and outputs occur on the falling edge. SinceLthe device is static, the
D
clock frequency may be any value between 0 and 20 MH5z and may be interrupted at
C
2
any time.
Hold: TheE/HOLD pin is used when the host CPU must interrupt a memory operation
M
/HOLD
W
F
for another task. When /HOLD is low, the current operation is suspended. The device
R
:
ignores any transition on SCK or /CS. All transitions on /HOLD must occur while
E
e
SCK is low.
v
/WP
SI
Input
Input
Write Protect: This active low pin prevents write operations to the status register only.
i
T
N
A complete explanation of write ptrotection is provided on pages 6 and 7.
Serial Input: All data is inpuat to the device on this pin. The pin is sampled on the
O
n
rising edge of SCK and is ignored at other times. It should always be driven to a valid
r
R
logic level to meet IDD specifications.
e
N
t
l
* SI may be connected to SO for a single pin data interface.
O
SO
Output
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
A
F
the falling edge of the serial clock.
* SO may be connected to SI for a single pin data interface.
Power Supply (3.0V to 3.6V)
VDD
VSS
Supply
Supply
Ground
Rev. 2.3
March 2007
Page 2 of 14
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
