HD64F2149 Datasheet, PDF (716/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

22.7.3 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 22.13.
The wait times (x, y, z, α, β, γ, ε, η, θ) after setting/clearing individual bits in flash memory
control registers 1 and 2 (FLMCR1, FLMCR2) and the maximum number of erase (N) are shown
in section 25, Electrical Characteristics, 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) µs 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 + β) ms 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) µs 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.
22.7.4 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, then the
ESU bit in FLMCR2 is cleared at least (α) µs later), the watchdog timer is cleared after the elapse
of (β) µs 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) µs 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) µs 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) µs. If erasure has been completed on all the erase blocks,
clear the SWE bit in FLMCR1, and wait (θ) µs. 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.
682