465
15.7.4
Erase Mode
To erase an individual flash memory block, follow the erase/erase-verify flowchart (single-block
erase) shown in figure 15.12.
To perform data or program erasure, make a 1-bit setting for the flash memory area to be erased in
erase block register 1 or 2 (EBR1, EBR2) at least (t
sswe
)
µ
s after setting the SWE bit to 1 in flash
memory control register 1 (FLMCR1). Next, set up the watchdog timer to prevent overerasing in
the event of program runaway, etc. Set a value greater than (t
se
) ms + (t
sesu
+ t
ce
+ t
cesu
)
µ
s as the
WDT overflow period. After this, preparation for erase mode (erase setup) is carried out by setting
the ESU bit in FLMCR1, and after the elapse of (t
cesu
)
µ
s or more, the operating mode is switched
to erase mode by setting the E bit in FLMCR1. The time during which the E bit is set is the flash
memory erase time. Ensure that the erase time does not exceed (t
se
) ms.
Note:
With flash memory erasing, preprogramming (setting all memory data in the memory to
be erased to all "0") is not necessary before starting the erase procedure.
15.7.5
Erase-Verify Mode
In erase-verify mode, data is read after memory has been erased to check whether it has been
correctly erased.
After the elapse of a the erase time, erase mode is exited (the E bit in FLMCR1 is cleared, then the
ESU bit is cleared at least (t
ce
)
µ
s later), the watchdog timer is cleared, and the operating mode is
switched to erase-verify mode by setting the EV bit in FLMCR. Before reading in erase-verify
mode, a dummy write of H'FF data should be made to the addresses to be read. The dummy write
should be executed after the elapse of (t
sev
)
µ
s or more. When the flash memory is read in this state
(verify data is read in 16-bit units), the data at the latched address is read. Wait at least (t
sevr
)
µ
s
after the dummy write before performing this read operation. If the read data has been erased (all
"1"), a dummy write is performed to the next address, and erase-verify is performed. If the read
data is unerased, set erase mode again and repeat the erase/erase-verify sequence in the same way.
However, ensure that the erase/erase-verify sequence is not repeated more than (N) times. When
verification is completed, exit erase-verify mode, and wait for at least (t
cev
)
µ
s. If erasure has been
completed on all the erase blocks, clear the SWE bit in FLMCR1. If there are any unerased blocks,
make a 1 bit setting for the flash memory area to be erased, and repeat the erase/erase-verify
sequence as before.
Leave a wait time of at least (t
cswe
)
µ
s after clearing SWE.