M3885 datasheet(82/103 Pages) RENESAS

82 / 103 page

3885 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

Fig. 77 Flash memory control registers

Fig. 78 CPU rewrite mode set/reset flowchart

Flash memory control register (address 0FFE16)

FMCR

RY/BY status flag (FMCR0)

0: Busy (being programmed or erased)

1: Ready

CPU reprogram mode select bit (FMCR1) (Note 2)

0: Normal mode (Software commands invalid)

1: CPU rewrite mode (Software commands acceptable)

CPU reprogram mode entry flag (FMCR2)

0: Normal mode

1: CPU rewrite mode

Flash memory reset bit (FMCR3) (Note 3)

0: Normal operation

1: Reset

User ROM area / Boot ROM area select bit (FMCR4) (Note 4)

0: User ROM area accessed

1: Boot ROM area accessed

Reserved bits (Indefinite at read/ “0” at write)

Notes1: The contents of flash memory control register are “XXX00001” just after reset release.

2: For this bit to be set to “1”, the user needs to write “0” and then “1” to it in succession. If it is not

this procedure, this bit will not be set to ”1”. Additionally, it is required to ensure that no interrupt

will be generated during that interval.

Use the control program in the area except the built-in flash memory for write to this bit.

3: This bit is valid when the CPU rewrite mode select bit is “1”. Set this bit 3 to “0” subsequently after

setting bit 3 to “1”.

4: Use the control program in the area except the built-in flash memory for write to this bit.

End

Start

Execute read array command or reset flash

memory by setting flash memory reset bit (by

writing “1” and then “0” in succession) (Note 2)

Single-chip mode, or boot mode

Set CPU mode register (Note 1)

Using software command execute erase,

program, or other operation

Jump to transferred control program in RAM

(Subsequent operations are executed by control

program in this RAM)

Transfer CPU reprogram mode

control program to internal RAM

Notes 1: Set bit 6,7 (Main clock division ratio selection bits ) at CPU mode register (003B16).

2: Before exiting the CPU reprogram mode after completing erase or program operation, always be sure to

execute a read array command or reset the flash memory.

Write “0” to CPU reprogram mode select bit

Set CPU reprogram mode select bit to “1” (by

writing “0” and then “1” in succession)(Note 3)

Check the CPU reprogram mode entry flag

Program in ROM

Program in RAM

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