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Sector erase

Sector erase requires six bus cycles: two unlock write cycles, a setup command, two additional unlock

write cycles, and finally the sector erase command. Identify the sector to be erased by addressing any

location in the sector. The address is latched on the falling edge of WE; the command, 30h, is latched

on the rising edge of WE. The sector erase operation begins after a 80 µs time-out.

To erase multiple sectors, write the sector erase command to each of the addresses of sectors to erase

after following the six bus cycle operation above. Timing between writes of additional sectors must be

<80 µs, or the AS29F040 ignores the command and erasure begins. During the erase time-out period

any falling edge of WE resets the time-out. Any command (other than sector erase or erase suspend)

during the time-out period resets the AS29F040 to read mode, and the device ignores the sector erase

command string. Erase such ignored sectors by restarting the sector erase command on the ignored

sectors.

The entire array need not be written with 0s prior to erasure. AS29F040 writes 0s to the entire sector

prior to electrical erase; writing of 0s affects only selected sectors, leaving non-selected sectors

unaffected. AS29F040 requires no CPU control or timing signals during sector erase operations.

Automatic sector erase begins after erase time-out from the last rising edge of WE from the sector erase

command stream and ends when the DATA polling (DQ7) is logical 1. DATA polling must be performed

on addresses that fall within the sectors being erased. AS29F040 returns to read mode after sector erase

unless DQ5 is set high by exceeding the time limit.

Erase suspend

Erase suspend allows interruption of sector erase operations to perform data reads from or writes to

a sector not being erased. Erase suspend applies only during sector erase operations, including the time-

out period. Writing an erase suspend command during sector erase time-out results in immediate

termination of the time-out period and suspension of erase operation.

AS29F040 ignores any commands during erase suspend other than read/reset, program, or erase

resume commands. Writing the Erase Resume command continues erase operations. Addresses are

DON’T CARE when writing Erase suspend or Erase resume commands.

AS29F040 takes 0.2–15 µs to suspend erase operations after receiving erase suspend command. To

determine completion of erase suspend, check DQ6 after selecting an address of a sector not being

erased. Check DQ2 in conjunction with DQ6 to determine if a sector is being erased. AS29F040

ignores redundant writes of erase suspend.

While in erase-suspend mode AS29F040 allows reading data (erase-suspend-read mode) from or

programming data (erase-suspend-program mode) to any sector not undergoing sector erase, treated as

standard read or standard programming mode. AS29F040 defaults to erase-suspend-read mode while

an erase operation has been suspended.

Write the resume command 30h to continue operation of sector erase. AS29F040 ignores redundant

writes of the resume command. AS29F040 permits multiple suspend/resume operations during sector

erase.

Sector protect

When attempting to write to a protected sector, DATA polling andToggle Bit 1 (DQ6) are activated for

about <1 µs. When attempting to erase a protected sector, DATA polling andToggle Bit 1 (DQ6) are

activated for about <5 µs. In both cases, the device returns to read mode without altering the specified

sectors.

Item

Description