M30218 Datasheet, PDF (156/179 Pages) Mitsubishi Electric Semiconductor – M30218 Group

CPU Rewrite Mode
Mitsubishi microcomputers
M30218 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Microcomputer Mode and Boot Mode
The control program for CPU rewrite mode must be written into the user ROM or boot ROM area in
parallel I/O mode beforehand. (If the control program is written into the boot ROM area, the standard
serial I/O mode becomes unusable.)
See Figure AA-3 for details about the boot ROM area.
Normal microcomputer mode is entered when the microcomputer is reset with pulling CNVSS pin low
(VSS). In this case, the CPU starts operating using the control program in the user ROM area.
When the microcomputer is reset by pulling the P52 pin high (VCC), the CNVSS pin high(VPPH), the CPU
starts operating using the control program in the boot ROM area. This mode is called the “boot” mode.
The control program in the boot ROM area can also be used to rewrite the user ROM area.
CPU rewrite mode operation procedure
The internal flash memory can be operated on to program, read, verify, or erase it while being placed on-
board by writing commands from the CPU to the flash memory control register (addresses 03B416,
03B516) and flash command register (address 03B616). Note that when in CPU rewrite mode, the boot
ROM area cannot be accessed for program, read, verify, or erase operations. Before this can be accom-
plished, a CPU write control program must be written into the boot ROM area in parallel input/output
mode. The following shows a CPU rewrite mode operation procedure.
<Start procedure (Note 1)>
(1) Apply VPPH to the CNVSS/VPP pin and VCC to the port P46 pin for reset release. Or the user can
jump from the user ROM area to the boot ROM area using the JMP instruction and execute the CPU
write control program. In this case, set the CPU write mode select bit of the flash memory control
register to “1” before applying VPPH to the CNVSS/VPP pin.
(2) After transferring the CPU write control program from the boot ROM area to the internal RAM, jump
to this control program in RAM. (The operations described below are controlled by this program.)
(3) Set the CPU rewrite mode select bit to “1”.
(4) Read the CPU rewrite mode monitor flag to see that the CPU rewrite mode is enabled.
(5) Execute operation on the flash memory by writing software commands to the flash command regis-
ter.
Note 1: In addition to the above, various other operations need to be performed, such as for entering the
data to be written to flash memory from an external source (e.g., serial I/O), initializing the ports, and
writing to the watchdog timer.
<Clearing procedure>
(1) Apply VSS to the CNVSS/VPP pin.
(2) Set the CPU rewrite mode select bit to “0”.
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