M16CSLASH1N datasheet(187/238 Pages) RENESAS

187 / 238 page

Rev.1.00

Oct 20, 2004

page 175 of 222

M16C/1N Group

19. Flash Memory Version

REJ09B0007-0100Z

19.3 Functions to Inhibit Rewriting Flash Memory Version

To prevent the flash memory from being read or rewritten easily, parallel I/O mode has a ROM code

protect and standard serial I/O and CAN I/O modes have an ID code check function.

19.3.1 ROM code protect function

The ROM code protect function inhibits the flash memory from being read or rewritten during parallel

I/O mode. Figure 19.2 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 by clearing one or both of two ROMCP1 bits to "0" when the ROMCR

bits are not '002,' with the flash memory thereby protected against reading or rewriting. Conversely,

when the ROMCR bits are '002' (ROM code protect removed), the flash memory can be read or

rewritten. Once the ROM code protect function is enabled, the ROMCR bits cannot be changed during

parallel I/O mode. Therefore, use standard serial I/O or other modes to rewrite the flash memory.

19.3.2 ID code check function

Use this function in standard serial I/O and CAN I/O modes. Unless the flash memory is blank, the ID

codes sent from the programmer and the 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 accepted.

The ID code consists of 8-bit data, the areas of which, beginning with the first byte, are 0FFFDF16,

0FFFE316, 0FFFEB16, 0FFFEF16, 0FFFF316, 0FFFF716, and 0FFFFB16. Prepare a program in which

the ID codes are preset at these addresses and write it in the flash memory.

Figure 19.3 shows ID code store addresses.

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