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7542 Group
Functions To Inhibit Rewriting Flash
Memory Version
To prevent the contents of internal flash memory from being read
out or rewritten easily, this MCU incorporates a ROM code protect
function for use in parallel I/O mode and an ID code check func-
tion for use in standard serial I/O mode.
(1) ROM Code Protect Function
The ROM code protect function is the function to inhibit reading
out or modifying the contents of internal flash memory by using
the ROM code protect control address (address FFDB
lel I/O mode. Figure 102 shows the ROM code protect control
address (address FFDB
). (This address exists in the User ROM
16
area.)
b7
Notes
1: When ROM code protect is turned on, the internal flash memory is protected
against readout or modification in parallel I/O mode.
2: When ROM code protect level 2 is turned on, ROM code readout by a
shipment inspection LSI tester, etc. also is inhibited.
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
modified in parallel I/O mode, they need to be rewritten in serial I/O mode or CPU
rewrite mode.
Fig. 102 Structure of ROM code protect control address
Rev.3.02
Oct 31, 2006
REJ03B0006-0302
) in paral-
16
b0
ROM code protect control address (address FFDB
1 1
ROMCP (FF
Reserved bits ("1" at read/write)
ROM code protect level 2 set bits (ROMCP2) (Notes 1, 2)
b3b2
0 0: Protect enabled
0 1: Protect enabled
1 0: Protect enabled
1 1: Protect disabled
ROM code protect reset bits (Note 3)
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 1)
b7b6
0 0: Protect enabled
0 1: Protect enabled
1 0: Protect enabled
1 1: Protect disabled
Page 81 of 134
If one or both of the pair of ROM code protect bits is set to "0", the
ROM code protect is turned on, so that the contents of internal
flash memory are protected against readout and modification. The
ROM code protect is implemented in two levels. If level 2 is se-
lected, 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", the
ROM code protect is turned off, so that the contents of internal
flash memory can be readout or modified. Once the 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
CPU rewrite mode to rewrite the contents of the ROM code protect
reset bits.
Rewriting of only the ROM code protect control address (address
FFDB
) cannot be performed. When rewriting the ROM code pro-
16
tect reset bit, rewrite the whole user ROM area (block 0)
containing the ROM code protect control address.
when shipped)
16
)
16
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