
R01UH0218EJ0110 Rev.1.10
Page 135 of 664
Sep 12, 2011
R32C/142 Group and R32C/145 Group
7. Clock Generator
7.9
Notes on Clock Generator
7.9.1
Sub Clock
7.9.1.1
Oscillator Constant Matching
The constant matching of the sub clock oscillator should be evaluated in both cases when the drive
power is high and low.
Contact the oscillator manufacturer for details on the oscillation circuit constant matching.
7.9.2
Power Control
Do not switch the base clock source until the oscillation of the clock to be used has stabilized. However,
this does not apply to the on-chip oscillator since it starts running immediately after the CM31 bit in the
CM3 register is set to 1.
To switch the base clock source from the PLL clock to a low speed clock, use the MOV.L or OR.L
instruction to set the BCS bit in the CCR register to 1.
Program example in assembly language
OR.L
#80h, 0004h
Program example in C language
asm("OR.L #80h, 0004h");
7.9.2.1
Stop Mode
To exit stop mode using a reset, apply a low signal to the
RESET pin until the main clock oscillation
stabilizes.
7.9.2.2
Suggestions for Power Saving
The followings are suggestions to reduce power consumption when programming or designing
systems.
I/O pins:
If inputs are floating, both transistors may be conducting. Set unassigned pins to input mode and
connect each of them to VSS via a resistor, or set them to output mode and leave them open.
A/D converter:
When not performing the A/D conversion, set the VCUT bit in the AD0CON1 register to 0 (VREF
disconnected). To perform the A/D conversion, set the VCUT bit to 1 (VREF connected) and wait at
least 1 s before starting conversion.
D/A converter:
When not performing the D/A conversion, set the DAiE bit in the DACON register (i = 0, 1) to 0
(output disabled) and the DAi register to 00h.
Peripheral clock stop:
When entering wait mode, power consumption can be reduced by setting the CM02 bit in the CM0
register to 1 to stop the peripheral clock source. However, this setting does not stop the fC32.