![](http://datasheet.mmic.net.cn/260000/PSD413A1F_datasheet_15952827/PSD413A1F_89.png)
PSD413F Family
6-89
ADVANCE INFORMATION
Command
Definitions
(cont.)
Chip Erase
Chip erase is a six bus cycle operation. There are two “unlock” write cycles. These are
followed by writing the “set-up” command. Two more “unlock” write cycles are then followed
by the chip erase command.
The chip erase command should not be used on devices that use sector erase
commands. Likewise, sector erase commands should not be used on devices that
use the chip erase command.
Chip erase does not require the user to program the device prior to erase. Upon executing
the Embedded Erase Algorithm command sequence the device will automatically program
and verify the entire memory for an all zero data pattern prior to electrical erase. The erase
is performed concurrently on all sectors at the same time (see Table 5 “Erase and
Programming Performance” for erase times). 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 WRF 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 mode.
Figure 2 illustrates the Embedded Erase Algorithm using typical command strings and bus
operations.
Sector Erase
Sector erase is a six bus cycle operation. There are two “unlock” write cycles. These are
followed by 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 WRF, while the command (30H) is latched on the
rising edge of WRF. After a time-out of 80 μs from the rising edge of the last sector erase
command, the sector erase operation will begin.
Multiple sectors may be erased concurrently by writing the six bus cycle operations as
described 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 80 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 interrupts can be re-enabled after the last Sector Erase command is written.
A time-out of 80 μs from the rising edge of the last WRF will initiate the execution of the
Sector Erase command(s). If another falling edge of the WRF occurs within the 80 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 during this period will reset the device to read mode, ignoring the previous
command string. In that case, restart the erase on those sectors and allow them to
complete.
(Refer to the Write Operation Status Section for DQ3, Sector Erase Timer operation).
Loading the sector erase buffer may be done in any sequence and with any number of
sectors (0 to 7).
If the multiple sector erase command is used, multiple sectors should be erased in
groups to ensure that a group of sectors is exposed to the same number of
program/erase cycles. In addition, the chip erase command should not be used on a
device that uses sector erase or multiple sector erase commands.
Sector erase does not require the user to program the device prior to erase. The device
automatically programs all memory locations in the sector(s) to be erased prior to electrical
erase. When erasing a sector or sectors the remaining unselected sectors ane not affected.
The system is not required to provide any controls or timings during these operations.