M37517F8HP Datasheet, PDF (62/98 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7517 Group
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
During CPU rewrite mode, set the internal clock φ 4.0 MHz or
less using the main clock division ratio selection bits (bit 6, 7 at
003B16).
(2) Instructions inhibited against use
The instructions which refer to the internal data of the flash
memory cannot be used during CPU rewrite mode .
(3) Interrupts inhibited against use
The interrupts cannot be used during CPU rewrite mode be-
cause they refer to the internal data of the flash memory.
(4) Watchdog timer
In case of the watchdog timer has been running already, the in-
ternal reset generated by watchdog timer underflow does not
happen, because of watchdog timer is always clearing during
program or erase operation.
(5) Reset
Reset is always valid. In case of CNVSS = H when reset is re-
leased, boot mode is active. So the program starts from the ad-
dress contained in address FFFC16 and FFFD16 in boot ROM
area.
Rev.1.01 Aug 02, 2004 page 62 of 96