M306H7MG-XXXFP Datasheet, PDF (322/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
19. USAGE NOTES
19.11.11 How to access
To set the FMR01, FMR02, or FMR11 bit to “1”, write “0” and then “1” in succession. This is necessary to
ensure that no interrupts or DMA transfers will occur before writing “1” after writing “0”. Also only when NMI
pin is “H” level.
19.11.12 Writing in the user ROM area
EW0 Mode
• If the power supply voltage drops while rewriting any block in which the rewrite control program is stored,
a problem may occur that the rewrite control program is not correctly rewritten and, consequently, the flash
memory becomes unable to be rewritten thereafter. In this case, standard serial I/O or parallel I/O mode
should be used.
EW1 Mode
• Avoid rewriting any block in which the rewrite control program is stored.
19.11.13 DMA transfer
In EW1 mode, make sure that no DMA transfers will occur while the FMR0 register’s FMR00 bit = 0
(during the auto program or auto erase period).
19.11.14 Regarding Programming/Erasure Times and Execution Time
As the number of programming/erasure times increases, so does the execution time for software commands
(Program, Block Erase, and Lock Bit Program). Especially when the number of programming/erasure times
exceeds 100, the software command execution time is noticeably extended.
Therefore, the software command wait time that is set must be greater than the maximum rated value of
electrical characteristics.
The software commands are aborted by hardware reset 1, NMI interrupt, and watchdog timer interrupt. If a
software command is aborted by such reset or interrupt, the block that was in process must be erased before
reexecuting the aborted command.
Rev.2.10 Oct 25, 2006 Page 322 of 326
REJ03B0152-0210