Rev.6.00 Oct.28.2004 page 596
of 1016
REJ09B0138-0600H
19.9.3
Erase Mode
Flash memory erasing should be performed block by block following the procedure shown in the erase/erase-verify
flowchart (single-block erase) shown in figure 19-20.
The wait times (x, y, z,
α
, ß,
γ, ε, η)
after bits are set or cleared in flash memory control registers 1 and 2 (FLMCR1,
FLMCR2) and the maximum number of programming operations (N) are shown in table 22.42 in section 22.7.6, Flash
Memory Characteristics.
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 or EBR2) at least (x)
µ
s after setting the SWE bit to 1 in flash memory control register 1 (FLMCR1). Next, the
watchdog timer is set to prevent overerasing in the event of program runaway, etc. Set a value greater than (y + z +
α
+ ß)
µ
s as the WDT overflow period. After this, preparation for erase mode (erase setup) is carried out by setting the ESU bit in
FLMCR2, and after the elapse of (y)
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 (z) ms.
Note:
With flash memory erasing, preprogramming (setting all data in the memory to be erased to 0) is not necessary
before starting the erase procedure.
19.9.4
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 the erase time, erase mode is exited (the E bit in FLMCR1 is cleared to 0, then the ESU bit in FLMCR2
is cleared to 0 at least (
α
)
µ
s later), the watchdog timer is cleared after the elapse of (
β
)
µ
s or more, and the operating
mode is switched to erase-verify mode by setting the EV bit in FLMCR1. 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 (
γ
)
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 (
ε
)
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 has not been erased,
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 (
η
)
µ
s. If erasure has been completed on all the erase blocks, clear the SWE bit in FLMCR1 to 0. If there are any
unerased blocks, make a 1 bit setting in EBR1 or EBR2 for the flash memory area to be erased, and repeat the erase/erase-
verify sequence in the same way.
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