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PSD4256G6V
This is preliminary information on a new product now in dev elopment or under going evaluation. Details are subject to change without notice.
ERASING FLASH MEMORY
Flash Bulk Erase
The Flash Bulk Erase inst ruction us es six WRITE
operations followed by a READ operation of the
status register, as described in Table 29, page 27.
If any byte o f the Bulk Era se instru ction is wrong,
the Bulk Erase instruction aborts and the device is
reset to the READ Memo ry mode.
During a Bulk Erase, the memory status may be
checked by reading the Error Flag Bit (DQ5/
DQ13), the Toggle F lag Bit (D Q6/DQ14), and t he
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
(maximu m number of Erase cycl e s have b een ex-
ecuted).
It is not necessary to program the memory with
00h because the PSD automatically does this be-
fore erasing to 0FFh.
During execut ion of the Bulk Erase instruction, the
Flash mem ory does not accept any instructions.
Flash Sector Erase
The Sector E rase instruction us es six WRITE op-
erations, as descr ibed in Tabl e 29, page 27. Addi-
tional Flash Sector Erase conf irm 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 tran smitted in a shorter
time than the tim e-out period o f about 10 0µ s . The
input of a new Sector Erase command restarts the
time-out period.
The status of the interna l timer can be monitored
through the level of the Erase Time-out Flag Bit
(DQ3/DQ11). If the Erase Time-out F lag 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 current ly in progress, and re-
set the device to READ Mod e. 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 F lag Bit (D Q6/DQ14), and t he
Data Polling Bit (DQ7/DQ15), as detailed in the
section entitled “PROGRAMMING FLASH MEM-
ORY”, on page 31.
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 mem ory 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 approp riate Sector Select (FS0-
FS15 or CSBOO T0-CSB OO T3) is High. (See Ta-
ble 29, page 27). This allows reading of data from
another Flash memor y sector aft er the Erase cycle
has been suspended. Suspend Sector Erase is
accepted only during the Flash Sector Erase in-
struction executi on and defaults to READ Mode. A
Suspend Sector Erase instruction executed during
an Erase time-o ut pe riod, 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 th is bit m ust be m onitored at an address
within t he Flas h 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 ex ecuted. 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 se ctor
that was being erased outputs invalid data.
– Reading from a Flash memory sector that was
not
being erased is valid.
– The Flash memory
cannot
be program med, and
only responds t o Resume Sec tor Erase and RE-
SET instructions (READ is an operation and is
allowed).
–If a RESET
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 , th e Erase c ycle may be resumed
with this instruction. The Resume Sector Erase in-
struction con sists of wri ting 030h t o any even ad-
dress while an appropriate Sector Select (FS0-
FS15 or CSBOO T0-CSB OO T3) is High. (S ee Ta-
ble 29, page 27.)