R8C/20 Group, R8C/21 Group 19. Flash Memory
Rev.2.00 Aug 27, 2008 Page 380 of 458
REJ09B0250-0200
19.3 Functions to Prevent Rewriting of Flash Memory
Standard serial I/O mode contains an ID code check function, and the parallel I/O mode contains a ROM code
protect function to prevent the flash memory from reading or rewriting easily.
19.3.1 ID Code Check Function
Use this function in standard serial I/O mode. Unless the flash memory is blank, the ID codes sent from the
programmer and the ID codes written in the flash memory are determined whether 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, the areas of which, beginning with the first byte, are 00FFDFh, 00FFE3h, 00FFEBh, 00FFEFh, 00FFF3h,
00FFF7h, and 00FFFBh. Write a program in which the ID codes are set at these addresses and write them in the
flash memory.
Figure 19.3 Address for Stored ID Code
4 bytes
Address
00FFDFh to 00FFDCh Undefined instruction vector
NOTE:
1. The OFS register is assigned to 00FFFFh. Refer to
Figure 19.4 OFS Register for the OFS register
details.
Overflow vector
00FFE3h to 00FFE0h
00FFE7h to 00FFE4h
BRK instruction vector
Address match vector
00FFEBh to 00FFE8h
00FFEFh to 00FFECh
Oscillation stop detection/watchdog
timer/voltage monitor 2 vector
00FFF3h to 00FFF0h
00FFF7h to 00FFF4h
Address break
00FFFBh to 00FFF8h
Reset vector
00FFFFh to 00FFFCh
(Reserved)
ID1
ID2
ID3
ID4
ID5
ID6
ID7
(1)
Single step vector
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