SA25C020 Datasheet, PDF (20/31 Pages) List of Unclassifed Manufacturers – 2Mb EEPROM with 25MHz SPI Bus Interface

Write Enable (WREN)
The device powers up in the Write Disable
state when V_CC is applied. All programming
instructions must be preceded by a WREN
instruction. The instruction sequence is
shown in Figure 11, with SO in high
impedance.
CS
SA25C020 Advanced Information
SAIFUN
20
Write Disable (WRDI)
To protect the device against inadvertent
writes, the WRDI instruction disables all
programming modes. The WRDI
instruction is independent of the WP pin's
status. The WREN instruction should be
executed after the WRDI instruction to
re-enable all programming modes. The
instruction sequence is shown in Figure 12,
with SO in high impedance.
SCK
01 234 567
Instruction
SI
Figure 11. Write Enable (WREN) Instruction Sequence
CS
SCK
01234567
Instruction
SI
Figure 12. Write Disable (WRDI) Instruction Sequence