Renesas M16C/26 Series Reference Book page 28

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
M16C/26 Group
1.10.7 Operation speed
Before entering CPU rewrite mode (EW0 or EW1 mode), select 10 MHz or less for CPU clock using the
CM0 register's CM06 bit and CM1 register's CM17–6 bits. Also, set the PM1 register's PM17 bit to 1 (with
wait state).
1.10.8 Instructions inhibited against use
The following instructions cannot be used in EW0 mode because the flash memory's internal data is
referenced: UND instruction, INTO instruction, JMPS instruction, JSRS instruction, and BRK instruction
1.10.9 Interrupts
EW0 Mode
• Any interrupt which has a vector in the variable vector table can be used providing that its vector is
transferred into the RAM area.
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• The NMI and watchdog timer interrupts can be used because the FMR0 register and FMR1 regis-
ter are initialized when one of those interrupts occurs. The jump addresses for those interrupt
service routines should be set in the fixed vector table.
Because the rewrite operation is halted when a NMI or watchdog timer interrupt occurs, the rewrite
program must be executed again after exiting the interrupt service routine.
• The address match interrupt cannot be used because the flash memory's internal data is refer-
enced.
EW1 Mode
• Make sure that any interrupt which has a vector in the variable vector table or address match
interrupt will not be accepted during the auto program or auto erase period.
• Avoid using watchdog timer interrupts.
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• The NMI interrupt can be used because the FMR0 register and FMR1 register are initialized when
this interrupt occurs. The jump address for the interrupt service routine should be set in the fixed
vector table.
Because the rewrite operation is halted when a NMI interrupt occurs, the rewrite program must be
executed again after exiting the interrupt service routine.
1.10.10 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 DMA transfers will occur before writing "1" after writing "0". Also when PM24 is "0" (P8
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function(NMI disable)) or when PM24 is "1" (NMI function) and NMI pin is "H" level.
1.10.11 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, conse-
quently, 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.
Rev.0.90 2003.12.28 page 23 of 28
1.10 Precautions for Flash Memory Version
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