PSD835G2V_07 Datasheet, PDF (41/118 Pages) STMicroelectronics – Flash PSD, 3 V supply, for 8-bit MCUs 4 Mbit + 256 Kbit dual Flash memories and 64 Kbit SRAM

PSD835G2V
9
Erasing Flash memory
Erasing Flash memory
9.1
Flash Bulk Erase
The Flash Bulk Erase instruction uses six Write operations followed by a Read operation of
the status register, as described in Table 28. on page 32. If any byte of the Bulk Erase
instruction is wrong, the Bulk Erase instruction aborts and the device is reset to the Read
Flash memory status.
During a Bulk Erase, the memory status may be checked by reading the Error Flag (DQ5)
bit, the Toggle Flag (DQ6) bit, and the Data Polling Flag (DQ7) bit, as detailed in
Programming Flash memory on page 37. The Error Flag (DQ5) bit returns a 1 if there has
been an Erase Failure (maximum number of Erase cycles has been executed).
It is not necessary to program the memory with 00h because the PSD automatically does
this before erasing to 0FFh.
During execution of the Bulk Erase instruction, the Flash memory does not accept any
instructions.
9.2
Flash Sector Erase
The Sector Erase instruction uses six Write operations, as described in Table 28. on page
32. Additional Flash Sector Erase codes and Flash memory sector addresses can be written
subsequently to erase other Flash memory sectors in parallel, without further coded cycles,
if the additional bytes are transmitted in a shorter time than the time-out period of about 100
µs. The input of a new Sector Erase code restarts the time-out period.
The status of the internal timer can be monitored through the level of the Erase Time-out
Flag (DQ3) bit. If the Erase Time-out Flag (DQ3) bit is 0, the Sector Erase instruction has
been received and the time-out period is counting. If the Erase Time-out Flag (DQ3) bit is 1,
the time-out period has expired and the PSD is busy erasing the Flash memory sector(s).
Before and during Erase time-out, any instruction other than Suspend Sector Erase and
Resume Sector Erase instructions abort the cycle that is currently in progress, and reset the
device to Read mode. It is not necessary to program the Flash memory sector with 00h as
the PSD does this automatically before erasing (Byte=FFh).
During a Sector Erase, the memory status may be checked by reading the Error Flag (DQ5)
bit, the Toggle Flag (DQ6) bit, and the Data Polling Flag (DQ7) bit, as detailed in
Programming Flash memory on page 37.
During execution of the Erase cycle, the Flash memory accepts only Reset and Suspend
Sector Erase instructions. Erasure of one Flash memory sector may be suspended, in order
to read data from another Flash memory sector, and then resumed.
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