M16C28 Datasheet, PDF (396/423 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/28 Group (M16C/28, M16C/28B)
20. Precautions
20.14.9 Interrupts
EW Mode 0
• 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 register
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 referenced.
EW Mode 1
• Make sure that any interrupt which has a vector in the variable vector table or address match inter-
rupt will not be accepted during the auto program period or auto erase period with erase-suspend
function disabled.
_______
• 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.
20.14.10 How to Access
To set the FMR01, FMR02, FMR11 or FMR16 bit to “1”, set the subject bit to “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 the bit to “1”. When the PM24 bit is set to “1” (NMI funciton), apply a high-level (“H”)
_______
signal to the NMI pin to set those bits.
20.14.11 Writing in the User ROM Area
EW Mode 0
• 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.
EW Mode 1
• Avoid rewriting any block in which the rewrite control program is stored.
20.14.12 DMA Transfer
In EW mode 1, make sure that no DMA transfers will occur while the FMR00 bit in the FMR0 register is set
to "0"(during the auto program or auto erase period).
20.14.13 Regarding Programming/Erasure Times and Execution Time
As the number of programming/erasure times increases, so does the execution time for software com-
mands (Program, and Block Erase).
_______
The software commands are aborted by hardware reset 1, hardware reset 2, NMI interrupt, and watchdog
timer interrupt. If a software command is aborted by such reset or interrupt, the affected block must be
erased before reexecuting the aborted command.
Rev. 2.00 Jan. 31, 2007 ^{page 376} of 385
REJ09B0047-0200