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Item
Description
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.
Sector erase
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 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.
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.
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.
Sector protect
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ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
