M16CSLASH29 datasheet(369/499 Pages) RENESAS

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20. Flash Memory Version

page 345

20.6 Precautions in CPU Rewrite Mode

Described below are the precautions to be observed when rewriting the flash memory in CPU rewrite mode.

20.6.1 Operation Speed

When the CPU clock source is the main clock, set the CPU clock frequency at 10 MHz or less with the

CM06 bit in the CM0 register and bits CM17 and CM16 in the CM1 register, before entering CPU rewrite

mode (EW mode 0 or EW mode 1). Also, when selecting f3(ROC) of a on-chip oscillator as a CPU clock

source, set bits ROCR3 and ROCR2 in the ROCR register to the CPU clock division rate at “divide-by-4”

or “divide-by-8”, before entering CPU rewrite mode (EW mode 0 or EW mode 1).

In both cases, set the PM17 bit in the PM1 register to 1 (with wait state).

20.6.2 Prohibited Instructions

The following instructions cannot be used in EW mode 0 because the CPU tries to read data in the flash

memory: UND instruction, INTO instruction, JMPS instruction, JSRS instruction, and BRK instruction

20.6.3 Interrupts

EW Mode 0

• To use interrupts having vectors in a relocatable vector table, the vectors must be relocated to the

RAM area.

_______

• The NMI and watchdog timer interrupts are available since registers FMR0 and FMR1 are forcibly

reset when either interrupt occurs. However, the interrupt program, which allocates the jump

addresses for each interrupt routine to the fixed vector table, is needed. Flash memory rewrite

_______

operation is aborted when the NMI or watchdog timer interrupt occurs. Set the FMR01 bit to 1 and

execute the rewrite and erase program again after exiting the interrupt routine.

• The address match interrupt can not be used since the CPU tries to read data in the flash memory.

EW Mode 1

• Do not acknowledge any interrupts with vectors in the relocatable vector table or the address

match interrupt during the auto program period or auto erase period with erase-suspend function

disabled.

20.6.4 How to Access

To set bit FMR01, FMR02, FMR11 or FMR16 to 1, write 1 immediately after setting to 0. Do not generate

an interrupt or a DMA transfer between the instruction to set the bit to 0 and the instruction to set it to 1.

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_______ _____

When the NMI function is selected, set the bit while an “H” signal is applied to the P85/NMI/SD pin.

20.6.5 Writing in the User ROM Area

20.6.5.1 EW Mode 0

• If the supply voltage drops while rewriting the block where the rewrite control program is stored,

the flash memory can not be rewritten, because the rewrite control program is not correctly rewrit-

ten. If this error occurs, rewrite the user ROM area in standard serial I/O mode or parallel I/O

mode.

20.6.5.2 EW Mode 1

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

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