M16C6S_09 Datasheet, PDF (163/208 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6S Group
Flash Memory Version
Boot Mode
After a hardware reset which is performed by applying a high-level signal to the CNVSS and P15 pins, the
microcomputer is placed in boot mode, thereby executing the program in the boot ROM area.
The boot ROM area contains a standard serial input/output mode based rewrite control program which was
stored in it when shipped from the factory.
Functions To Prevent Flash Memory from Rewriting
To prevent the flash memory from being read or rewritten easily, parallel input/output mode has a ROM
code protect and standard serial input/output mode has an ID code check function.
• ROM Code Protect Function
The ROM code protect function inhibits the flash memory from being read or rewritten during parallel
input/output mode. Figure 1.20.3 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 input/output
mode. Therefore, use standard serial input/output or other modes to rewrite the flash memory.
• ID Code Check Function
Use this function in standard serial input/output mode. 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.
Rev.5.01 Dec 10, 2009 page 163 of 201
REJ03B0014-0501