ST & T UPSD3212C - Manual (Page 100)

uPSD3212A, uPSD3212C, uPSD3212CV
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Erasing Flash Memory
Flash Bulk Erase. The Flash Bulk Erase instruc-
tion uses six WRITE operations followed by a
READ operation of the status register, as de-
scribed in
Table 82. 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 Bit (DQ5), the
Toggle Flag Bit (DQ6), and the Data Polling Flag
Bit (DQ7), as detailed in
Programming Flash
Memory, page 98 . The Error Flag Bit (DQ5) re-
turns a '1' if there has been an Erase Failure (max-
imum number of Erase cycles have been
executed).
It is not necessary to program the memory with
00h because the PSD MODULE automatically
does this before erasing to 0FFh.
During execution of the Bulk Erase instruction, the
Flash memory does not accept any instructions.
Flash Sector Erase. The Sector Erase instruc-
tion uses six WRITE operations, as described in
Table 82., page 95 . 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 100µs. 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 Bit
(DQ3). If the Erase Time-out Flag Bit (DQ3) is '0,'
the Sector Erase instruction has been received
and the time-out period is counting. If the Erase
Time-out Flag Bit (DQ3) is '1,' the time-out period
has expired and the embedded algorithm 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.
During a Sector Erase, the memory status may be
checked by reading the Error Flag Bit (DQ5), the
Toggle Flag Bit (DQ6), and the Data Polling Flag
Bit (DQ7), as detailed in
Programming Flash
Memory, page 98 .
During execution of the Erase cycle, the Flash
memory accepts only RESET and Suspend Sec-
tor Erase instructions. Erasure of one Flash mem-
ory sector may be suspended, in order to read
data from another Flash memory sector, and then
resumed.
Suspend Sector Erase. When a Sector Erase
cycle is in progress, the Suspend Sector Erase in-
struction can be used to suspend the cycle by writ-
ing 0B0h to any address when an appropriate
Sector Select (FS0-FS3 or CSBOOT0-CSBOOT1)
is High. (See
Table 82., page 95 ). This allows
reading of data from another Flash memory sector
after the Erase cycle has been suspended. Sus-
pend Sector Erase is accepted only during an
Erase cycle and defaults to READ Mode. A Sus-
pend Sector Erase instruction executed during an
Erase time-out period, in addition to suspending
the Erase cycle, terminates the time out period.
The Toggle Flag Bit (DQ6) stops toggling when the
internal logic is suspended. The status of this bit
must be monitored at an address within the Flash
memory sector being erased. The Toggle Flag Bit
(DQ6) stops toggling between 0.1µs and 15µs af-
ter the Suspend Sector Erase instruction has been
executed. The Flash memory is then automatically
set to READ Mode.
If an Suspend Sector Erase instruction was exe-
cuted, the following rules apply:
–
Attempting to read from a Flash memory
sector that was being erased outputs invalid
data.
– Reading from a Flash sector that was not
being erased is valid.
– The Flash memory cannot be programmed,
and only responds to Resume Sector Erase
and Reset Flash instructions (READ is an
operation and is allowed).
– If a Reset Flash instruction is received, data in
the Flash memory sector that was being
erased is invalid.
Resume Sector Erase. If a Suspend Sector
Erase instruction was previously executed, the
erase cycle may be resumed with this instruction.
The Resume Sector Erase instruction consists of
writing 030h to any address while an appropriate
Sector Select (FS0-FS3 or CSBOOT0-CSBOOT1)
is High. (See
Table 82., page 95 .)