AT26F004_06 Datasheet, PDF (13/38 Pages) ATMEL Corporation – 4-megabit 2.7-volt Only Serial Firmware DataFlash Memory

AT26F004
9. Protection Commands and Features
9.1 Write Enable
The Write Enable command is used to set the Write Enable Latch (WEL) bit in the Status Regis-
ter to a logical “1” state. The WEL bit must be set before a program, erase, Protect Sector,
Unprotect Sector, or Write Status Register command can be executed. This makes the issuance
of these commands a two step process, thereby reducing the chances of a command being
accidentally or erroneously executed. If the WEL bit in the Status Register is not set prior to the
issuance of one of these commands, then the command will not be executed.
To issue the Write Enable command, the CS pin must first be asserted and the opcode of 06h
must be clocked into the device. No address bytes need to be clocked into the device, and any
data clocked in after the opcode will be ignored. When the CS pin is deasserted, the WEL bit in
the Status Register will be set to a logical “1”. The complete opcode must be clocked into the
device before the CS pin is deasserted; otherwise, the device will abort the operation and the
state of the WEL bit will not change.
Figure 9-1. Write Enable
CS
SCK
SI
SO
01234567
OPCODE
00000110
MSB
HIGH-IMPEDANCE
13
3588C–DFLASH–04/06