PSD4235G2V-10U STMICROELECTRONICS [STMicroelectronics], PSD4235G2V-10U Datasheet - Page 33

• Manufacturer Part Number: PSD4235G2V-10U
• Description: Flash In-System Programmable (ISP) Peripherals for 16-bit MCUs
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ERASING FLASH MEMORY
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 29, page 27.
If any byte of the Bulk Erase instruction is wrong,
the Bulk Erase instruction aborts and the device is
reset to the READ Memory mode.
During a Bulk Erase, the memory status may be
checked by reading the Error Flag Bit (DQ5/
DQ13), the Toggle Flag Bit (DQ6/DQ14), and the
Data Polling Bit (DQ7/DQ15), as detailed in the
section entitled “PROGRAMMING FLASH MEM-
ORY”, on page 31. The Error Flag Bit (DQ5/DQ13)
returns a '1' if there has been an Erase Failure
(maximum number of Erase cycles have been ex-
ecuted).
It is not necessary to program the memory with
00h because the PSD automatically does this be-
fore erasing to 0FFh.
During execution of the Bulk Erase instruction, the
Flash memory does not accept any instructions.
Flash Sector Erase
The Sector Erase instruction uses six WRITE op-
erations, as described in Table 29, page 27. Addi-
tional Flash Sector Erase confirm commands and
Flash memory sector addresses can be written
subsequently to erase other Flash memory sec-
tors in parallel, without further coded cycles, if the
additional commands are transmitted in a shorter
time than the time-out period of about 100µs. The
input of a new Sector Erase command 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/DQ11). If the Erase Time-out Flag Bit (DQ3/
DQ11) is '0,' the Sector Erase instruction has been
received and the time-out period is counting. If the
Erase Time-out Flag Bit (DQ3/DQ11) 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,
abort the cycle that is currently in progress, and re-
set 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.
During a Sector Erase, the memory status may be
checked by reading the Error Flag Bit (DQ5/
DQ13), the Toggle Flag Bit (DQ6/DQ14), and the
Data Polling Bit (DQ7/DQ15), as detailed in the
section entitled “PROGRAMMING FLASH MEM-
ORY”, on page 31.
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.
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 Sus-
pend Sector Erase instruction can be used to sus-
pend the cycle by writing 0B0h to any even
address when an appropriate Sector Select (FS0-
FS15 or CSBOOT0-CSBOOT3) is High. (See Ta-
ble 29, page 27). This allows reading of data from
another Flash memory sector after the Erase cycle
has been suspended. Suspend Sector Erase is
accepted only during the Flash Sector Erase in-
struction execution and defaults to READ Mode. A
Suspend Sector Erase instruction executed during
an Erase time-out period, in addition to suspend-
ing the Erase cycle, terminates the time out period.
The Toggle Flag Bit (DQ6/DQ14) stops toggling
when the PSD 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/DQ14) stops toggling be-
tween 0.1µs and 15µs after the Suspend Sector
Erase instruction has been executed. The PSD 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
– Reading from a Flash memory sector that was
– The Flash memory cannot be programmed, and
– If a RESET instruction is received, data in the
Resume Sector Erase
If a Suspend Sector Erase instruction was previ-
ously executed, the Erase cycle may be resumed
with this instruction. The Resume Sector Erase in-
struction consists of writing 030h to any even ad-
dress while an appropriate Sector Select (FS0-
FS15 or CSBOOT0-CSBOOT3) is High. (See Ta-
ble 29, page 27.)
that was being erased outputs invalid data.
not being erased is valid.
only responds to Resume Sector Erase and RE-
SET instructions (READ is an operation and is
allowed).
Flash memory sector that was being erased is
invalid.
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