M30222 Datasheet, PDF (187/237 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

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Specifications in this manual are tentative and subject to change
MITSUBISHI MICROCOMPUTERS
M30222 Group
Rev. G
CPU Rewrite Mode (Flash Memory Version)
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
CPU Rewrite Mode
In CPU rewrite mode, the on-chip flash memory can be operated on (read, program, or erase) under
control of the Central Processing Unit (CPU). Only the user ROM area shown in Figure 1.149 can be
rewritten; the boot ROM area cannot be rewritten. Make sure the program and block erase commands
are issued for only the user ROM area and each block area.
The control program for CPU rewrite mode can be stored in either user ROM or boot ROM area. In the
CPU rewrite mode, because the flash memory cannot be read from the CPU, the rewrite control pro-
gram must be transferred to RAM memory before it can be executed.
Microcomputer Mode and Boot Mode
Normal microcomputer mode is entered when the microcomputer is reset with pulling CNVss pin low.
In this case, the CPU starts executing the control program in the user ROM area. When the microcom-
puter is reset and both the CNVss pin and P74 (CE) pin are pulled high, the CPU starts operating using
the control program in the boot ROM area (program start address is C000016, 7D00016). This mode is
called the "boot" mode.
The control program for CPU rewrite mode must be written into the user ROM or boot ROM area
beforehand. (If the control program is written into the boot ROM area, standard serial I/O mode be-
comes unusable.) See Figure 1.149 for details about the boot ROM area.
Block Address
Block addresses refer to the maximum even address of each block. These addresses are used in the
block erase command.
Outline Performance
In the CPU rewrite mode, the CPU erases, programs, and reads the internal flash memory as in-
structed by software commands. This rewrite control program must be transferred to internal RAM
before it can be executed.
The CPU rewrite mode is accessed by writing "1" for the CPU rewrite mode select bit (bit 1 in address
034B416). Software commands are accepted once the mode is accessed.
In the CPU rewrite mode, software commands are used to write and read data into even-numbered
addresses ("0" for byte address A0) in 16-bit units. Always write 8-bit software comands into even-
numbered address. Commands are ignored with odd-numbered addresses.
Use software commands to control program and erase operations. Whether a program or erase op-
eration has terminated normally or in error can be verified by reading the status register. Figure 1.150
shows the flash memory control register.
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