11.2.16 Sector Erase (20h)
The sector Erase instruction sets all memory within a specified sector (4K-bytes) to the erased
state of all 1s (FFh). A Write Enable instruction must be executed before the device will accept the
Sector Erase Instruction (Status Register bit WEL must equal 1). The instruction is initiated by
driving the /CS pin low and shifting the instruction code “20h” followed a 24-bit sector address
(A23-A0). The Sector Erase instruction sequence is shown in figure 16.
The /CS pin must be driven high after the eighth bit of the last byte has been latched. If this is not
done the Sector Erase instruction will not be executed. After /CS is driven high, the self-timed
Sector Erase instruction will commence for a time duration of tSE (See AC Characteristics). While
the Sector Erase cycle is in progress, the Read Status Register instruction may still be accessed
for checking the status of the BUSY bit. The BUSY bit is a 1 during the Sector Erase cycle and
becomes a 0 when the cycle is finished and the device is ready to accept other instructions again.
After the Sector Erase cycle has finished the Write Enable Latch (WEL) bit in Status Register is
cleared to 0. The Sector Erase instruction will not be executed if the addressed page is protected
by the Block Protect (SEC, TB, BP2, BP1, and BP0) bits (see Status Register Memory protection
Figure 16. Sector Erase Instruction Sequence Diagram