PSD813F2 datasheet(27/110 Pages) STMICROELECTRONICS

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PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2

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 9., page 21.

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 the section entitled PRO-

GRAMMING FLASH MEMORY, page 25. The Er-

ror Flag Bit (DQ5) returns a '1' if there has been an

Erase Failure (maximum number of Erase cycles

have been executed).

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 9., page 21. Addi-

tional Flash Sector Erase codes and Flash

memory sector addresses can be written subse-

quently to erase other Flash memory sectors in

parallel, without further coded cycles, if the addi-

tional 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 peri-

od.

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 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 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

(byte = FFh).

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 the section entitled PRO-

GRAMMING FLASH MEMORY, page 25.

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 re-

sumed.

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 address

when an appropriate Sector Select (FS0-FS7 or

CSBOOT0-CSBOOT3)

High.

(See

Table

9., page 21). This allows reading of data from an-

other Flash memory sector after the Erase cycle

has been suspended. Suspend Sector Erase is

accepted only during an Erase cycle and defaults

to READ Mode. A Suspend Sector Erase instruc-

tion 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

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) stops toggling between 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 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 previ-

ously executed, the erase cycle may be resumed

with this instruction. The Resume Sector Erase in-

struction consists of writing 030h to any address

while an appropriate Sector Select (FS0-FS7 or

CSBOOT0-CSBOOT3)

High.

(See

Table

9., page 21.)

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