Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Functions To Inhibit Rewriting (Flash Memory Version)
Functions To Inhibit Rewriting Flash Memory Version
To prevent the contents of the flash memory version from being read out or rewritten easily, the device
incorporates a ROM code protect function for use in parallel I/O mode and an ID code check function for
use in standard serial I/O mode.
ROM code protect function
The ROM code protect function reading out or modifying the contents of the flash memory version by
using the ROM code protect control address (0FFFFF16) during parallel I/O mode. Figure 1.29.9 shows
the ROM code protect control address (0FFFFF16). (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 version are protected against readout and modification. ROM code protect is imple-
mented in two levels. If level 2 is selected, the flash memory is protected even against readout by a
shipment inspection LSI tester, etc. 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 version can be read out or modified. 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 the serial I/
O or some other mode to rewrite the contents of the ROM code protect reset bits.
ROM code protect control address
Symbol
ROMCP
Address
0FFFFF16
When reset
FF16
b7 b6 b5 b4 b3 b2 b1 b0
Bit symbol
Bit name
Function
Always set this bit to 1.
Reserved bit
b3 b2
ROM code protect level
2 set bit (Note 1, 2)
ROMCP2
00: Protect enabled
01: Protect enabled
10: Protect enabled
11: Protect disabled
b5 b4
ROM code protect reset
bit (Note 3)
ROMCR
00: Protect removed
01: Protect set bit effective
10: Protect set bit effective
11: Protect set bit effective
b7 b6
ROM code protect level
1 set bit (Note 1)
ROMCP1
00: Protect enabled
01: Protect enabled
10: Protect enabled
11: Protect disabled
Note 1: When ROM code protect is turned on, the on-chip flash memory is protected against
readout or modification in parallel input/output mode.
Note 2: When ROM code protect level 2 is turned on, ROM code readout by a shipment
inspection LSI tester, etc. also is inhibited.
Note 3: 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 changed in parallel input/
output mode, they need to be rewritten in serial input/output or some other mode.
Figure 1.29.9. ROM code protect control address
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MITSUBISHI [ Mitsubishi Group ]
