M16C80 Datasheet, PDF (289/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
30. CPU Rewrite Mode
Program in ROM
Start
Transfer the program to be executed in the
low speed mode, to the internal RAM.
Jump to transferred control program in RAM
(Subsequent operations are executed by control
program in this RAM)
*1
Program in RAM
*1
Set flash memory power supply-OFF bit to “1”
(by writing “0” and then “1” in succession)(Note 1)
Switch the count source of BCLK.
XIN stop. (Note 2)
Process of low speed mode
XIN oscillating Wait until the XIN has stabilized
Switch the count source of BCLK (Note 2)
Set flash memory power supply-OFF bit to “0”
Wait time until the internal circuit stabilizes
(Set NOP instruction about twice)
End
Note 1: For flash memory power supply-OFF bit to be set to “1”, the user needs to write a “0” and then a “1” to it in
succession. When it is not this procedure, it is not enacted in “1”. This is necessary to ensure that no
interrupt or DMA transfer will be executed during the interval.
Note 2: Before the count source for BCLK can be changed from XIN to XCIN or vice versa, the clock to which
the count source is going to be switched must be oscillating stably.
Figure 30.3 Shifting to the low speed mode flowchart
Rev.1.00 Aug. 02, 2005 ^{Page 278} of 329
REJ09B0187-0100