S-25A640A Datasheet, PDF (14/32 Pages) Seiko Instruments Inc – Function to prevent malfunction by monitoring clock pulse

FOR AUTOMOTIVE 125°C OPERATION SPI SERIAL E²PROM
S-25A640A, S-25A640B
Rev.3.2_01
1. 2 BP1, BP0 (b3, b2) : Block Protect
Bit BP1 and BP0 are composed of the nonvolatile memory. The area size of Software Protect against WRITE
instruction is defined by them. Rewriting these bits is possible by the WRSR instruction. To protect the memory
area against the WRITE instruction, set either or both of bit BP1 and BP0 to "1". Rewriting bit BP1 and BP0 is
possible unless they are in Hardware Protect mode. Refer to " Protect Operation" for details of Block Protect.
1. 3 WEL (b1) : Write Enable Latch
Bit WEL shows the status of internal Write Enable Latch. Bit WEL is set by the WREN instruction only. If bit WEL
is "1", this is the status that Write Enable Latch is set. If bit WEL is "0", Write Enable Latch is in reset, so that this
IC does not receive the WRITE or WRSR instruction. Bit WEL is reset after these operations;
• The power supply voltage is dropping
• At power-on
• After performing WRDI
• After the completion of write operation by the WRSR instruction
• After the completion of write operation by the WRITE instruction
1. 4 WIP (b0) : Write In Progress
Bit WIP is read only and shows whether the internal memory is in the write operation or not by the WRITE or
WRSR instruction. Bit WIP is "1" during the write operation but "0" during any other status. Figure 11 shows the
usage example.
CS
WRITE or WRSR instruction
RDSR instruction
RDSR instruction
RDSR instruction
D2 D1 D0
RDSR
SI
RDSR
S
R ^BB
W ^PP
D ¹⁰
S
R ^BB
W ^PP
D ¹⁰
SO
000 11
000 11
WEL, WIP
WEL, WIP
tPR
RDSR
S
R ^BB
W ^PP
D ¹⁰
000 ₀₀
WEL, WIP
Figure 11 Usage Example of WEL, WIP Bits during Write
2. Write enable (WREN)
Before writing data (WRITE and WRSR), be sure to set bit Write Enable Latch (WEL). This instruction is to set bit
WEL. Its operation is below.
After selecting this IC by the chip select ( CS ), input the instruction code from serial data input (SI). To set bit WEL,
set this IC in the non-select status by CS at the 8th clock of the serial clock (SCK). To cancel the WREN instruction,
input the clock different from a specified value (n = 8 clock) while CS is in "L".
14