AS29F400
Preliminary information
®
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 AS29F400 ignores the command and erasure begins. During the
80 µs time-out period any falling edge of WE resets the time-out. Any command (other than
Sector Erase or Erase Suspend) during time-out period resets the AS29F400 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. AS29F400 writes 0s to the entire
sector prior to electrical erase; writing of 0s affects only selected sectors, leaving non-selected
sectors unaffected. AS29F400 requires no CPU control or timing signals during sector erase
operations.
Automatic sector erase begins after 80 µs 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 address
must be performed on addresses that fall within the sectors being erased. AS29F400 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 read data from or program data 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.
AS29F400 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.
AS29F400 takes 0.1–15 µs to suspend erase operations after receiving Erase Suspend command. To
determine completion of erase suspend, either check DQ6 after selecting an address of a sector not
being erased, or poll RY/BY. Check DQ2 in conjunction with DQ6 to determine if a sector is
being erased. AS29F400 ignores redundant writes of Erase Suspend.
Erase Suspend
While in erase-suspend mode, AS29F400 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. AS29F400 defaults to erase-suspend-read
mode while an erase operation has been suspended.
Write the Resume command 30h to continue operation of sector erase. AS29F400 ignores
redundant writes of the Resume command. AS29F400 permits multiple suspend/resume
operations during sector erase.
When attempting to write to a protected sector, DATA polling and Toggle Bit 1 (DQ6) are
activated for about <1 µs. When attempting to erase a protected sector, DATA polling and
Toggle 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
Ready/Busy
RY/BY indicates whether an automated on-chip algorithm is in progress (RY/BY = low) or
completed (RY/BY = high). The device does not accept Program/Erase commands when
RY/BY = low. RY/BY= high when device is in erase suspend mode. RY/BY is an open drain
output, enabling multiple RY/BY pins to be tied in parallel with a pull up resistor to V
.
CC
7
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
