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M16C/29 Group
21.3 Functions To Prevent Flash Memory from Rewriting
The flash memory has a built-in ROM code protect function for parallel I/O mode and a built-in ID code
check function for standard input/output mode to prevent the flash memory from reading or rewriting.
21.3.1 ROM Code Protect Function
The ROM code protect function prevents the flash memory from reading and rewriting in parallel input/
output mode. Figure 21.3.1.1 shows the ROMCP register. The ROMCP register is located in the user
ROM area. The ROMCP1 bit consists of two bits. The ROM code protect function is enabled and reading
and rewriting flash memory is disabled when setting either or both of two ROMCP1 bits to "0" other than
the ROMCR bit is '00
rewritten. Once the ROM code protect function is enabled, the ROMCR bits can not be changed in paral-
lel input/output mode. Therefore, use the standard serial input/output or other modes to rewrite the flash
memory.
21.3.2 ID Code Check Function
Use the ID code check function in standard serial input/output mode. Unless the flash memory is blank,
the ID codes sent from the programmer and the seven bytes ID codes written in the flash memory are
compared to see if they match. If the ID codes do not match, the commands sent from the programmer
are not acknowledged. The ID code consists of 8-bit data, starting with the first byte, into addresses,
0FFFDF
, 0FFFE3
16
has a program with the ID code set in these addresses.
Rev.1.00 Nov 01,2004
REJ09B0101-0100Z
'. However, when setting the ROMCR bit to '00
2
, 0FFFEB
, 0FFFEF
16
16
page 370 of 402
, 0FFFF3
, 0FFFF7
16
16
16
21. Flash Memory Version
', the flash memory can be read or
2
, and 0FFFFB
. The flash memory
16
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