Chapter 19. Usage Notes - Renesas M16C Series Hardware Manual

R8C/11 Group
19. Usage Notes
19.1 Stop Mode and Wait Mode
19.1.1 Stop Mode
When entering stop mode, set the CM10 bit to "1" (stop mode) after setting the FMR01 bit to "0" (CPU
rewrite mode disabled). The instruction queue pre-reads 4 bytes from the instruction which sets the
CM10 bit in the CM1 register to "1" (stop mode) and the program stops. Insert at least 4 NOP instruc-
tions after inserting the JMP.B instruction immediately after the instruction which sets the CM10 bit to
"1".
Use the next program to enter stop mode.
• Program of entering stop mode
19.1.2 Wait Mode
When entering wait mode, execute the WAIT instruction after setting the FMR01 bit to "0" (CPU re-
write mode disabled). The instruction queue pre-reads 4 bytes from the WAIT instruction and the
program stops. Insert at least 4 NOP instructions after the WAIT instruction.
Also, the value in the specific internal RAM area may be rewritten when exiting wait mode if writing to
the interna RAM area before executing the WAIT instruction and entering wait mode. The area for a
maximum of 3 bytes is rewirtten from the following address of the internal RAM in which the writing is
performed before the WAIT instruction. If this causes a problem, avoid by inserting the JMP.B instruc-
tion between the writing instruction to the internal RAM area and WAIT instruction as shown in the
following program example.
• Example to execute WAIT instruction
Program Example
When accessing any area other than the internal RAM area between the writing instruction to the
internal RAM area and execution of the WAIT instruction, this situation will not occur.
Rev.1.20 Jan 27, 2006
REJ09B0062-0120
BCLR 1, FMR0
BSET 0, PRCR
BSET 0, CM1
JMP.B LABEL_001
LABEL_001:
NOP
NOP
NOP
NOP
MOV.B #055h,0601h
•••
JMP.B LABEL_001
LABEL_001 :
FSET I
BCLR 1,FMR0
WAIT
NOP
NOP
NOP
NOP
page 186 of 204
; CPU rewrite mode disabled
; Protect exited
; Stop mode
; Write to internal RAM area
; Interrupt enabled
; CPU rewrite mode disabled
; Wait mode
19. Usage Notes