M3885 datasheet(87/103 Pages) RENESAS

87 / 103 page

3885 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

Functions To Inhibit Rewriting Flash Memory

To prevent the contents of the flash memory data from being read

out or rewritten easily, the device incorporates a ROM code protect

function for use in parallel I/O mode.

ROM code protect function

The ROM code protect function is the function inhibit reading out or

modifying the contents of the flash memory version by using the

ROM code protect control address (FFDB16) during parallel I/O

mode. Figure 82 shows the ROM code protect control address

(FFDB16). (This address exists in the user ROM area.)

If one of the pair of ROM code protect bits is set to “0”, ROM code

protect is turned on, so that the contents of the flash memory data

are protected against readout and reprogram. ROM code protect is

implemented in two levels. If level 2 is selected, the flash memory is

protected even against readout by a manufactures inspection test

also. When an attempt is made to select both level 1 and level 2,

level 2 is selected by default.

If both of the two ROM code protect reset bits are set to “00”, ROM

code protect is turned off, so that the contents of the flash memory

data can be read out or reprogram. Once ROM code protect is

turned on, the contents of the ROM code protect reset bits cannot

be modified in parallel I/O mode. Use CPU reprogram mode to re-

program the contents of the ROM code protect reset bits.

Fig. 82 ROM code protect control address

ROM code protect control (address FFDB16) (Note 1)

ROMCP

Reserved bits (“1” at read/write)

ROM code protect level 2 set bits (ROMCP2) (Notes 2, 3)

b3b2

0 0: Protect enabled

0 1: Protect enabled

1 0: Protect enabled

1 1: Protect disabled

ROM code protect reset bits (ROMCR) (Note 4)

b5b4

0 0: Protect removed

0 1: Protect set bits effective

1 0: Protect set bits effective

1 1: Protect set bits effective

ROM code protect level 1 set bits (ROMCP1) (Note 2)

b7b6

0 0: Protect enabled

0 1: Protect enabled

1 0: Protect enabled

1 1: Protect disabled

Notes 1: The contents of ROM code protect control register are “FF16” just after reset

release. This area is on the ROM in the mask ROM version.

2: When ROM code protect is turned on, the internal flash memory is protected

against readout or modification in parallel I/O mode.

3: When ROM code protect level 2 is turned on, ROM code readout by a shipment

inspection LSI tester, etc. also is inhibited.

4: The ROM code protect reset bits can be used to turn off ROM code protect level 1

and ROM code protect level 2. However, since these bits cannot be modified in

parallel I/O mode, they need to be rewritten in standard serial I/O mode or CPU

rewrite mode.

M3885 Datasheet(PDF) 87 Page - Renesas Technology Corp

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