S-25A010A Datasheet, PDF (18/35 Pages) Seiko Instruments Inc – Write protect function during the low power supply voltage

FOR AUTOMOTIVE 125°C OPERATION SPI SERIAL E²PROM
S-25A010A/020A/040A
Rev.5.2_01
5. Write in the status register (WRSR)
The values of status register (BP1, BP0) can be rewritten by inputting the WRSR instruction. But b7, b6, b5, b4, b1,
b0 of status register cannot be rewritten. b7 to b4 are always "1" when reading the status register.
Before inputting the WRSR instruction, set bit WEL by the WREN instruction. The operation of WRSR is shown
below.
Set the chip select ( CS ) "L" first. After that, input the instruction code and data from serial data input (SI). To start
WRSR write (tPR), set the chip select ( CS ) to "H" after inputting data or before inputting a rising of the next serial
clock. It is possible to confirm the operation status by reading the value of bit WIP during WRSR write. Bit WIP is "1"
during write, "0" during any other status. Bit WEL is reset when write is completed.
With the WRSR instruction, the values of BP1 and BP0; which determine the area size the users can handle as the
read only memory; can be changed. When WP pin is "L", however, the WRSR instruction is not be performed
(Refer to " Protect Operation").
Bits BP1 and BP0 keep the value which is the one prior to the WRSR instruction during the WRSR instruction. The
newly updated value is changed when the WRSR instruction has completed.
To cancel the WRSR instruction, input the clock different from a specified value (n = 16 clock) while CS is in "L".
CS
WP
High
SCK
SI
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Instruction
Inputs Data in the Status Register
X
b7 b6 b5 b4 b3 b2 b1 b0
SO
Remark X = Don't care.
High-Z
Figure 15 WRSR Operation
6. Read memory data (READ)
The READ operation is shown below. Input the instruction code and the address from serial data input (SI) after
inputting "L" to the chip select ( CS ). The input address is loaded to the internal address counter, and data in the
address is output from the serial data output (SO).
Next, by inputting the serial clock (SCK) keeping the chip select ( CS ) in "L", the address is automatically
incremented so that data in the following address is sequentially output. The address counter rolls over to the first
address by increment in the last address.
To finish the read cycle, set CS to "H". It is possible to raise the chip select always during the cycle. During write,
the READ instruction code is not be accepted or operated.
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