R8C/2C Group, R8C/2D Group
10. Clock Generation Circuit
Rev.2.00
Dec 05, 2007
REJ09B0339-0200
10.5.1.1
High-Speed Clock Mode
The XIN clock divided by 1 (no division), 2, 4, 8, or 16 provides the CPU clock. Set the CM06 bit to 1 (divide-
by-8 mode) when transiting to high-speed on-chip oscillator mode, low-speed on-chip oscillator mode. If the
CM14 bit is set to 0 (low-speed on-chip oscillator on) or the FRA00 bit in the FRA0 register is set to 1 (high-
speed on-chip oscillator on), fOCO can be used as timer RA. When the FRA00 bit is set to 1, fOCO40M can be
used as timer RC and timer RD. When the CM14 bit is set to 0 (low-speed on-chip oscillator on), fOCO-S can
be used for the watchdog timer and voltage detection circuit.
10.5.1.2
Low-Speed Clock Mode
The XCIN clock divided by 1 (no division) provides the CPU clock.
In this mode, stopping the XIN clock and high-speed on-chip oscillator, and setting the FMR47 bit in the FMR4
register to 1 (flash memory low consumption current read mode enabled) enables low consumption operation.
When the FRA00 bit is set to 1, fOCO40M can be used as timer RC and timer RD. When the CM14 bit is set to
0 (low-speed on-chip oscillator on), fOCO-S can be used for the watchdog timer and voltage detection circuit.
To enter wait mode from low-speed clock mode, setting the VCA20 bit in the VCA2 register to 1 (internal
power low consumption enabled) enables lower consumption current in wait mode.
10.5.1.3
High-Speed On-Chip Oscillator Mode
The high-speed on-chip oscillator is used as the on-chip oscillator clock when the FRA00 bit in the FRA0
register is set to 1 (high-speed on-chip oscillator on) and the FRA01 bit in the FRA0 register is set to 1. The on-
chip oscillator divided by 1 (no division), 2, 4, 8, or 16 provides the CPU clock. Set the CM06 bit to 1 (divide-
by-8 mode) when transiting to high-speed clock mode. If the FRA00 bit is set to 1, fOCO40M can be used as
timer RC and timer RD. When the CM14 bit is set to 0 (low-speed on-chip oscillator on), fOCO-S can be used
for the watchdog timer and voltage detection circuit.
10.5.1.4
Low-Speed On-Chip Oscillator Mode
If the CM14 bit in the CM1 register is set to 0 (low-speed on-chip oscillator on) or the FRA01bit in the FRA0
register is set to 0, the low-speed on-chip oscillator provides the on-chip oscillator clock.
The on-chip oscillator clock divided by 1 (no division), 2, 4, 8 or 16 provides the CPU clock. The on-chip
oscillator clock is also the clock source for the peripheral function clocks. Set the CM06 bit to 1 (divide-by-8
mode) when transiting to high-speed clock mode. When the FRA00 bit is set to 1, fOCO40M can be used as
timer RC and timer RD. When the CM14 bit is set to 0 (low-speed on-chip oscillator on), fOCO-S can be used
as the watchdog timer and voltage detection circuit.
In this mode, stopping the XIN clock and high-speed on-chip oscillator, and setting the FMR47 bit in the FMR4
register to 1 (flash memory low consumption current read mode enabled) enables low consumption operation.
To enter wait mode from low-speed on-chip oscillator mode, setting the VCA20 bit in the VCA2 register to 1
(internal power low consumption enabled) enables lower consumption current in wait mode.