M16C Datasheet, PDF (218/262 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Preliminary Specifications REV.B
Mitsubishi microcomputers
Specifications in this manual are tentative and subject to change.
M16C / 6N Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
CPU Rewrite Mode
Precautions on CPU Rewrite Mode
Described below are the precautions to observe when rewriting the flash memory in CPU rewrite
mode.
(1) Operation speed
When in CPU rewrite mode, set the main clock frequency as shown below, using the main clock
divide ratio select bit (bit 6 at address 000616 and bits 6 and 7 at address 000716):
6.25 MHz or less when wait bit (bit 7 at address 000516) is 0 (without internal access wait state)
12.5 MHz or less when wait bit (bit 7 at address 000516) is 1 (with internal access wait state)
(2) Instructions inhibited
The instructions listed below cannot be used when in CPU rewrite mode, because they refer to
the internal data of the flash memory:
UND instruction, INTO instruction, JMPS instruction, JSRS instruction and BRK instruction (when
using fixed vector table only)
(3) Interrupts inhibited
the NMI interrupt and address match interrupt cannot be used in CPU rewrite mode because they
refer to the internal flash memory. If interrupts have their in the INTB register, they can be used by
transferring the vector into the RAM area. The WDT interrupt can be used because the operation
mode is forcibly changed to normal mode when the interrupt is generated. Since the rewrite
operation is halted when the WDT interrupt occurs, the erase/program operation needs to be
performed over again.
(4) Internal reserved expansion bit (bit 3 at address 000516)
The reserved area of the internal memory can be changed by using the internal reserved
expansion bit (bit 3 at address 000516). However, if the CPU rewrite mode select bit (bit 1 at
address 03B716) is set to 1, the internal reserved expansion bit (bit 3 at address 000516) is also set
to 1 automatically. Similarly, if the CPU rewrite mode select bit (bit 1 at address 03B716) is set to 0,
the internal reserved bit (bit 3 at address 000516) also is set to 0 automatically.
(5) Reset
Reset input is always accepted. After a reset, the address 0C000016 through 0CFFFF16 are made
a reserved area and cannot be accessed. Therefore, if your product has this area in the user
ROM area, do not write any address of this area into the reset vector. This area is made
accessible by changing the internal reserved expansion bit (bit 3 at address 000516) in a program.
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