Flash Memory Version; Cpu Rewrite Mode - Renesas M16C FAMILY Hardware Manual

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
R8C/11 Group

19.6 Flash Memory Version

19.6.1 CPU Rewrite Mode

(1) Operation Speed
Before entering CPU rewrite mode (EW0 or EW1 mode), select 5 MHz or less for CPU clock using
the CM06 bit in the CM0 register and the CM16 to CM17 bits in the CM1 register.
(2) 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, and BRK instruction
(3) Interrupts
EW0 Mode
• Any interrupt which has a vector in the relocatable vector table can be used providing that its
vector is transferred into the RAM space.
• The watchdog timer and oscillation stop detection interrupts can be used because the FMR0
register and FMR1 register are initialized when one of those interrupts occurs. The jump ad-
dresses for those interrupt service routines should be set in the fixed vector table.
Because the rewrite operation is halted when a watchdog timer, oscillation stop detection or volt-
age detection interrupt occur, the rewrite program should be executed again after exiting the inter-
rupt 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 period or the auto erase period with erase-
suspend function disabled.
• Avoid using watchdog timer interrupts.
(4) How to Access
To set the FMR01, FMR02, or FMR11 bit to "1", write "0" and then "1" in succession. This is neces-
sary to ensure that no interrupts will occur before writing "1" after writing "0".
(5) Writing in User ROM Space
In 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, stan-
dard serial I/O or parallel I/O mode should be used.
(6) Wait Mode
When shifting to wait mode, set the FMR01 bit to "0" (CPU rewrite mode disabled) before executing
the WAIT instruction.
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19. Usage Notes