FM25H20-DG Ramtron, FM25H20-DG Datasheet - Page 5

• Manufacturer Part Number: FM25H20-DG
• Description: F-RAM 2Mb (256kX8) 3V
• Manufacturer: Ramtron

Specifications of FM25H20-DG

• Operating Supply Voltage: 2.7 V to 3.6 V
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: DFN-8
• Memory Size: 2Mbit
• Memory Configuration: 256K X 8
• Interface Type: Serial, SPI
• Supply Voltage Range: 2.7V To 3.6V
• Memory Case Style: TDFN
• No. Of Pins: 8
• Rohs Compliant: Yes
• Ic Interface Type: Serial, SPI
• Nvram Features: 2 Mbit Ferroelectric Nonvolatile RAM, Low Power Consumption, Write Protection Scheme
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Power Up to First Access
The FM25H20 is not accessible for a period of time
(1 ms) after power up. Users must comply with the
timing parameter t
from V
Data Transfer
All data transfers to and from the FM25H20 occur in
8-bit groups. They are synchronized to the clock
signal (C), and they transfer most significant bit
(MSB) first. Serial inputs are registered on the rising
edge of C. Outputs are driven from the falling edge of
C.
Command Structure
There are six commands called op-codes that can be
issued by the bus master to the FM25H20. They are
listed in the table below. These op-codes control the
functions performed by the memory. They can be
divided into three categories. First, there are
commands that have no subsequent operations. They
perform a single function such as to enable a write
operation. Second are commands followed by one
byte, either in or out. They operate on the Status
Register. The third group includes commands for
memory transactions followed by address and one or
more bytes of data.
Table 1. Op-code Commands
Rev. 2.2
Sept. 2010
Name
WREN
WRDI
RDSR
WRSR
READ
WRITE
SLEEP
DD
(min) to the first /S low.
D
Q
S
C
Description
Set Write Enable Latch
Write Disable
Read Status Register
Write Status Register
Read Memory Data
Write Memory Data
Enter Sleep Mode
PU
, which is the minimum time
0
0
0
1
Op-code
0000 0110b
0000 0100b
0000 0101b
0000 0001b
0000 0011b
0000 0010b
1011 1001b
Figure 5. WREN Bus Configuration
0
2
Hi-Z
3
0
4
0
WREN - Set Write Enable Latch
The FM25H20 will power up with writes disabled.
The WREN command must be issued prior to any
write operation. Sending the WREN op-code will
allow the user to issue subsequent op-codes for write
operations. These include writing the Status Register
(WRSR) and writing the memory (WRITE).
Sending the WREN op-code causes the internal Write
Enable Latch to be set. A flag bit in the Status
Register, called WEL, indicates the state of the latch.
WEL=1
Attempting to write the WEL bit in the Status
Register has no effect on the state of this bit – only
the WREN op-code can set this bit. The WEL bit will
be automatically cleared on the rising edge of /S
following a WRDI, a WRSR, or a WRITE operation.
This prevents further writes to the Status Register or
the F-RAM array without another WREN command.
Figure 5 below illustrates the WREN command bus
configuration.
WRDI - Write Disable
The WRDI command disables all write activity by
clearing the Write Enable Latch. The user can verify
that writes are disabled by reading the WEL bit in the
Status Register and verifying that WEL=0. Figure 6
illustrates the WRDI command bus configuration.
1
5
indicates
6
1
that
FM25H20 - 2Mb SPI FRAM
7
0
writes
are
Page 5 of 15
permitted.