16
MBM29F400TA/MBM29F400BA
Chip erase does not require the user to program the device prior to erase. Upon executing the Embedded EraseTM
Algorithm command sequence the device automatically will program and verify the entire memory f or an all zero
data pattern prior to electrical erase. The system is not required to provide any controls or timings during these
operations.
The automatic erase begins on the rising edge of the last WE pulse in the command sequence and terminates
when the data on DQ7 is “1” (See Write Operation Status section.) at which time the device returns to read the
mode.
Figure 16 illustrates the Embedded Erase Algorithm using typical command strings and bus operations.
Sector Erase
Sector erase is a six b us cycle oper ation. There are tw o “unlock” write cycles. These are followed b y writing the
“set-up” command. Two more “unlock” write cycles are then followed by the sector erase command. The sector
address (any address location within the desired sector) is latched on the falling edge of WE, while the command
(Data=30H) is latched on the rising edge of WE . A time-out of 50 µs from the rising edge of the last sector erase
command will initiate the sector erase command(s).
Multiple sectors may be erased sequentially by writing the six bus cycle operations as descr ibed above. This
sequence is followed with writes of the Sector Erase command to addresses in other sectors desired to be
concurrently erased. The time between writes must be less than 50 µs otherwise that command will not be
accepted and erasure will start. It is recommended that processor interrupts be disabled during this time to
guarantee this condition. The interr upts can be re-enabled after the last Sector Erase command is written. A
time-out of 50 µs from the rising edge of the last WE will initiate the e x ecution of the Sector Erase command(s).
If another falling edge of the WE occurs within the 50 µs time-out window the timer is reset. (Monitor DQ3 to
determine if the sector erase timer window is still open, see section DQ3, Sector Erase Timer.) Any command
other than Sector Erase or Erase Suspend during this time-out period will reset the device to the read mode,
ignoring the previous command string. Resetting the device once execution has begun will corrupt the data in
that sector. In that case, restart the erase on those sectors and allow them to complete. (Refer to the Write
Operation Status section f or Sector Erase Timer operation.) Loading the sector er ase buff er may be done in an y
sequence and with any number of sectors (0 to 10).
Sector erase does not require the user to progr am the de vice prior to erase. The de vice automatically progr ams
all memory locations in the sector(s) to be erased prior to electrical erase. When er asing a sector , the remaining
unselected sectors are not affected. The system is not required to provide any controls or timings during these
operations.
The automatic sector erase begins after the 50 µs time out from the rising edge of the WE pulse for the last
sector erase command pulse and terminates when the data on DQ7 is “1” (See Write Operation Status section.)
at which time the de vice returns to the read mode. Data polling must be perf ormed at an address within any of
the sectors being erased.
Figure 16 illustrates the Embedded Erase Algorithm using typical command strings and bus operations.
Erase Suspend
Erase Suspend command allows the user to interrupt the chip and then perf orm data reads (not program) from
a non-busy sector during a Sector Erase oper ation. (Which may take up to several seconds.) This command is
applicable ONLY during the Sector Erase operation and will be ignored if written during the chip Erase or
Programming operation. The Erase Suspend command (B0H) which is allowed only during the Sector Erase
Operation includes the sector erase time-out period after the Sector Erase commands (30H). Writing this
command during the time-out will result in immediate termination of the time-out period. An y subsequent writes
of the Sector Erase command will be taken as the Erase Resume command. Note that any other commands
during the time out will reset the device to read mode. The addresses are DON’T CARES when writing the Erase
Suspend or Erase Resume commands.
When the Erase Suspend command is written during a Sector Erase operation, the chip will take between 0.1
µs to 15 µs to suspend the erase operation and go into erase suspended read mode (pseudo-read mode), during