Datasheet

Section 17 ROM
Rev.7.00 Feb. 14, 2007 page 596 of 1108
REJ09B0089-0700
The flash memory itself cannot be read while the SWE bit is set to 1 to perform programming or
erasing, so the control program that performs programming and erasing should be run in on-chip
RAM or external memory. When the program is located in external memory, an instruction for
programming the flash memory and the following instruction should be located in on-chip RAM.
Figure 17.14 shows the procedure for executing the program/erase control program when
transferred to on-chip RAM.
Clear FWE*
FWE = high*
Branch to flash memory application
program
Branch to program/erase control
program in RAM area
Execute program/erase control
program (flash memory rewriting)
Transfer program/erase control
program to RAM
MD2, MD1, MD0 = 110, 111
Reset-start
Write the FWE assessment program and
transfer program (and the program/erase
control program if necessary) beforehand
Notes: Do not apply a constant high level to the FWE pin. Apply a high level to the FW
E pin
only when the flash memory is programmed or erased. Also, while a high level is
applied to the FWE pin, the watchdog timer should be activated to prevent
overprogramming or overerasing due to program runaway, etc.
* For further information on FWE application and disconnection, see section 17.12
,
Flash Memory Programming and Erasing Precautions.
Figure 17.14 User Program Mode Execution Procedure