M306H7MG-XXXFP Datasheet, PDF (282/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
17. FLASH MEMORY VERSION
17.3 Boot Mode
After a hardware reset which is performed by applying a low-level signal to the M1 pin and a high-level signal to
the CNVSS and P50 pins, the microcomputer is placed in boot mode, thereby executing the program in the boot
ROM area.
During boot mode, the boot ROM and user ROM areas are switched over by the FMR05 bit in the FMR0 register.
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.
The boot ROM area can be rewritten in parallel input/output mode. Prepare an EW0 mode based rewrite control
program and write it in the boot ROM area, and the flash memory can be rewritten as suitable for the system.
17.4 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.
17.4.1 ROM Code Protect Function
The ROM code protect function inhibits the flash memory from being read or rewritten during parallel input/
output mode. Figure 17.2 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 input/output mode. Therefore, use
standard serial input/output or other modes to rewrite the flash memory.
17.4.2 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.2.10 Oct 25, 2006 Page 282 of 326
REJ03B0152-0210