Erase Mode; Erase-Verify Mode - Renesas F-ZTAT H8 Series Hardware Manual

16-bit single-chip microcomputer

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Erase Mode

To erase the flash memory, follow the erasing algorithm shown in figure 19.10. This erasing

algorithm can erase data without subjecting the device to voltage stress or impairing the reliability

of programmed data.

To erase flash memory, before starting to erase, first place all memory data in all blocks to be

erased in the programmed state (program all memory data to H'00). If all memory data is not in the

programmed state, follow the sequence described later to program the memory data to zero. To

select the flash memory areas to be erased, first set the V

Next set the E bit in FLMCR, selecting erase mode. The erase time is the time during which the

E bit is set. To prevent overerasing, use a software timer to divide the erase time. Overerasing, due

to program runaway for example, can give memory cells a negative threshold voltage and cause

them to operate incorrectly. Before selecting erase mode, set up the watchdog timer so as to

prevent overerasing.

In program-verify mode, after data has been erased, it is read to check that it has been erased

correctly. After the erase time has elapsed, exit erase mode (clear the E bit to 0), select erase-

verify mode (set the EV bit to 1), and wait 4 µs. Before reading data in erase-verify mode, write

H'FF dummy data to the address to be read. This dummy write applies an erase-verify voltage to

the memory cells at the latched address. If the flash memory is read in this state, the data at the

latched address will be read. After the dummy write, wait 2 µs before reading. If the read data has

been successfully erased, perform the dummy write, wait 2 µs, and erase-verify for the next

address. If the read data has not been erased, select erase mode again and repeat the same erase

and erase-verify sequence through the last address, until all memory data has been erased to 1. Do

not repeat the erase and erase-verify sequence more than 602 times, however.

Section 19 Flash Memory (H8/3048F: Dual Power Supply (V

E bit in the flash memory control

Rev. 7.00 Sep 21, 2005 page 609 of 878

REJ09B0259-0700

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