Hitachi H8S/2646 Hardware Manual page 743

4. Do not apply a constant high level to the FWE pin.
Apply a high level to the FWE pin only when programming or erasing flash memory. A system
configuration in which a high level is constantly applied to the FWE pin should be avoided.
Also, while a high level is applied to the FWE pin, the watchdog timer should be activated to
prevent overprogramming or overerasing due to program runaway, etc.
5. Use the recommended algorithm when programming and erasing flash memory.
The recommended algorithm enables programming and erasing to be carried out without
subjecting the device to voltage stress or sacrificing program data reliability. When setting the
P or E bit in FLMCR1, the watchdog timer should be set beforehand as a precaution against
program runaway, etc.
6. Do not set or clear the SWE bit during execution of a program in flash memory.
Do not set or clear the SWE bit during execution of a program in flash memory. Wait for at
least 100 µs after clearing the SWE bit before executing a program or reading data in flash
memory. When the SWE bit is set, data in flash memory can be rewritten, but when SWE = 1,
flash memory can only be read in program-verify or erase-verify mode. Access flash memory
only for verify operations (verification during programming/erasing). Do not clear the SWE bit
during programming, erasing, or verifying.
Similarly, when using the RAM emulation function while a high level is being input to the
FWE pin, the SWE bit must be cleared before executing a program or reading data in flash
memory. However, the RAM area overlapping flash memory space can be read and written to
regardless of whether the SWE bit is set or cleared.
7. Do not use interrupts while flash memory is being programmed or erased.
All interrupt requests, including NMI, should be disabled during FWE application to give
priority to program/erase operations.
8. Do not perform additional programming. Erase the memory before reprogramming.
In on-board programming, perform only one programming operation on a 128-byte
programming unit block. In programmer mode, also, perform only one programming operation
on a 128-byte programming unit block. Further programming must only be executed after this
programming unit block has been erased.
9. Before programming, check that the chip is correctly mounted in the PROM
programmer.
Overcurrent damage to the device can result if the index marks on the PROM programmer
socket, socket adapter, and chip are not correctly aligned.
10. Do not touch the socket adapter or chip during programming.
Touching either of these can cause contact faults and write errors.
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