M37544 Datasheet, PDF (48/68 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7544 Group
ROM Code Access Protection
We would like to support a simple ROM code protection function
that prevents a party other than the ROM-code owner to read and
reprogram the builit-in PROM code of the MCU.
The MCU has 7 bytes of dedicated ROM spaces in address
0xFFD4 to 0xFFDA, as an ID-code (referred to as “the ID-code”)
enabling a Programmer to verify with the input ID-code and
validate further operations.
Expected Programmer ID-Code Verification
Function
First, Programmer must check the ID-code of the MCU.
If the ID-code is still in blank, Programmer enables all operations,
Read, Program, and Program-Verify.
When Programmer programs the MCU, Programmer also
programs the given ID-code as well as the actual firmware.
If the ID-code is not blank, Programmer verifies it with the input
ID-code.
When the ID-codes don't match, Programmer will reject all further
operations.
If they match, Programmer perform operations according to the
given command.
Address
FFD416
ID1
FFD516
ID2
FFD616
ID3
FFD716
ID4
FFD816
ID5
FFD916
ID6
FFDA16
ID7
Fig. 63 ROM-Code Protection ID Location
Rev.1.04 2004.06.08 page 48 of 66
REJ03B0012-0104Z