M16C6S_09 Datasheet, PDF (171/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Flash Memory Version
Precautions on CPU Rewrite Mode
Described below are the precautions to be observed when rewriting the flash memory in CPU rewrite mode.
(1) Operation Speed
Before entering CPU rewrite mode (EW0 or EW1 mode), select 10 MHz or less for BCLK using the
CM06 bit in the CM0 register and the CM17 to CM16 bits in the CM1 register. Also, set the PM17 bit in
the PM1 register to “1” (with wait state).
(2) Instructions to Prevent from Using
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 instruc-
tion
(3) 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.
_______
• 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.
• The WDT 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 WDT interrupt occurs, the rewrite program must be
executed again after exiting the interrupt service routine.
(4) 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”.
(5) Writing in the User ROM Space
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.5.01 Dec 10, 2009 page 171 of 201
REJ03B0014-0501