M32CSLASH8B datasheet(398/406 Pages) RENESAS

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M32C/8B Group

25. Usage Notes

Preliminary specification

Specifications in this manual are tentative and subject to change.

REJ09B0450-0050 Rev.0.50 Oct 31, 2008

Page 381 of 385

25.14 Flash Memory

25.14.1 Operating Speed

Prior to accessing registers FMR0 to FMR3 or to entering CPU rewrite mode (EW0, EW1 mode), set the CPU

clock frequency to 10 MHz or lower using bits MCD4 to MCD0 in the MCD register, and also set the PM12 bit

in the PM1 register to 1 (1 wait state).

25.14.2 Prohibited Instructions

The following instructions cannot be used in EW0 mode because the flash memory is accessed by executing

these instructions: UND, INTO, JMPS, JSRS, and BRK instructions.

25.14.3 Interrupts (EW0 Mode)

• To use peripheral function interrupts, place interrupt routine programs and the relocatable vector table in the

RAM area.

• When an interrupt request is generated by the NMI, watchdog timer, voltage monitor interrupt, or oscillation

stop detect function, registers FMR0, FMR1, and FMR3 are forcibly initialized and the erase or program

operation in progress is aborted. Now that the flash memory can be accessed, the interrupt routine will be

executed.

• The address match interrupt is not available because the flash memory is accessed to process this interrupt.

25.14.4 Interrupts (EW1 Mode)

• Do not generate a peripheral function interrupt or a DMA or DMACII transfer during an erase or program

operation.

• When an interrupt request is generated by the NMI, watchdog timer (when the PM22 bit is set to 1), voltage

monitor interrupt, or oscillation stop detect function, registers FMR0, FMR1, and FMR3 are forcibly initialized

and the erase or program operation in progress is aborted. Now that the flash memory can be accessed, the

interrupt routine will be executed.

25.14.5 How to Access

To set the FMR01 or FMR02 bit in the FMR0 register to 1, write a 1 immediately after writing a 0 to the bit.

Write to the FMR0 register in 8-bit units. Do not generate an interrupt or a DMA or DMACII transfer between

these two settings. Also, set these bits while a high-level (“H”) signal is applied to the NMI pin.

To change the FMR01 bit from 1 to 0, enter read array mode first, and then write into address 0057h in 16-bit

units. Set the eight high-order bits to 00h.

25.14.6 Rewriting User ROM Area (EW0 Mode)

If the supply voltage drops while rewriting the block where a rewrite control program is stored, it may not be

possible to rewrite the flash memory again, because the rewrite control program is not rewritten successfully. If

this happens, use standard serial I/O mode to rewrite the block.

25.14.7 Rewriting User ROM Area (EW1 Mode)

Do not rewrite a block where the rewrite control program is stored.

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