M30622M4 MITSUBISHI [Mitsubishi Electric Semiconductor], M30622M4 Datasheet - Page 249

• Manufacturer Part Number: M30622M4
• Description: SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
• Manufacturer: MITSUBISHI [Mitsubishi Electric Semiconductor]

Functions To Inhibit Rewriting (Flash Memory Version)
Functions To Inhibit Rewriting Flash Memory Version
Figure 1.29.9. ROM code protect control address
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 (0FFFFF
the ROM code protect control address (0FFFFF
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
b7
b6
b5
Note 1: When ROM code protect is turned on, the on-chip flash memory is protected against
Note 2: When ROM code protect level 2 is turned on, ROM code readout by a shipment
Note 3: The ROM code protect reset bits can be used to turn off ROM code protect level 1 and
b4
b3
readout or modification in parallel input/output mode.
inspection LSI tester, etc. also is inhibited.
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.
b2
b1
b0
Bit symbol
ROMCP2
ROMCP1
Reserved bit
ROMCR
Symbol
ROMCP
ROM code protect level
2 set bit (Note 1, 2)
ROM code protect reset
bit (Note 3)
ROM code protect level
1 set bit (Note 1)
0FFFFF
Address
Bit name
16
16
). (This address exists in the user ROM area.)
16
) during parallel I/O mode. Figure 1.29.9 shows
When reset
b5 b4
b3 b2
00: Protect enabled
01: Protect enabled
10: Protect enabled
11: Protect disabled
00: Protect removed
01: Protect set bit effective
10: Protect set bit effective
11: Protect set bit effective
b7 b6
00: Protect enabled
01: Protect enabled
10: Protect enabled
11: Protect disabled
FF
Always set this bit to 1.
16
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Function
Mitsubishi microcomputers
M16C / 62 Group
249