M32CSLASH86 datasheet(481/505 Pages) RENESAS

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Page 458

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27.5.6.2 Stop Mode

• Use the following procedure to select the main clock as the CPU clock when entering stop mode.

1) Set the CM17 bit in the CM1 register to "0" (main clock).

2) Set the CM21 bit in the CM2 register to "0" (clock selected by the CM17 bit).

3) Set the CM07 bit in the CM0 register to "0" (clock selected by the CM21 bit divided by the MCD

If the PLL clock is selected as the CPU clock source, set the CM17 bit to "0" (main clock) and the

PLC07 bit in the PLC0 register to "0" (PLL off) before entering stop mode.

______

• The microcomputer cannot enter stop mode if a low-level signal ("L") is applied to the NMI pin.

Apply a high-level ("H") signal instead.

____________

• If stop mode is exited by any reset, apply an "L" signal to the RESET pin until a main clock oscilla-

tion is stabilized enough.

______

• If using the NMI interrupt to exit stop mode, use the following procedure to set the CM10 bit in the

CM1 register (all clocks stopped).

______

1) Exit stop mode with using the NMI interrupt.

2) Generate a dummy interrupt.

3) Set the CM10 bit to "1".

e.g.,

int

#63

; dummy interrupt

bset

cm1

; all clocks stopped

/* dummy interrupt handling */

dummy

reit

• When entering stop mode, the instruction queue reads ahead to instructions following the instruc-

tion setting the CM10 bit in the CM1 register to "1" (all clocks stopped), and the program stops.

When the microcomputer exits stop mode, the instruction lined in the instruction queue is executed

before the interrupt routine for recovery is done.

Write the JMP.B instruction, as follows, after the instruction setting the CM10 bit in the CM1 register

to "1" (all clocks stopped).

e.g.,

bset 0, prcr

; protection removed

bset 0, cm1

; all clocks stopped

jmp.b LABEL_001

; JMP.B instruction executed (no instuction between JMP.B

; and LABEL.)

LABEL_001:

nop

; NOP (1)

nop

; NOP (2)

nop

; NOP (3)

nop

; NOP (4)

mov.b #0, prcr

; Protection set

•

27. Precautions (Clock Generation Circuit)

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