
Rev.2.10 Apr 14, 2006 page 70 of 378
REJ09B0124-0210
M16C/6N Group (M16C/6NK, M16C/6NM) 8. Clock Generation Circuit
8.4.1.6 On-chip Oscillator Mode
The on-chip oscillator clock divided by 1 (undivided), 2, 4, 8 or 16 provides the CPU clock. The on-chip
oscillator clock is also the clock source for the peripheral function clocks. If the sub clock is on, fC32 can
be used as the count source for timers A and B. When the operating mode is returned to the high-speed
and medium-speed modes, set the CM06 bit in the CM0 register to 1 (divide-by-8 mode).
8.4.1.7 On-chip Oscillator Low Power Dissipation Mode
The main clock is turned off after being placed in on-chip oscillator mode. The CPU clock can be
selected as in on-chip oscillator mode. The on-chip oscillator clock is the clock source for the peripheral
function clocks. If the sub clock is on, fC32 can be used as the count source for timers A and B.
Table 8.3 lists the Setting Clock Related Bit and Modes.
Table 8.3 Setting Clock Related Bit and Modes
Modes
CM2 Register
CM1 Register CM0 Register
CM21 CM11
CM17
,
CM16
CM07 CM06 CM05 CM04
PLL operating mode 0 1 00b 0 0 0 -
High-speed mode 0 0 00b 0 0 0 -
Medium-
Divide-by-2
0 0 01b 0 0 0 -
speed
Divide-by-4
0 0 10b 0 0 0 -
mode
Divide-by-8
00-0 10-
Divide-by-16
0 0 11b 0 0 0 -
Low-speed mode - 0 - 1 - 0 1
Low power 0 0 - 1 1
(1)
1
(1)
1
dissipation mode
On-chip
No division
1 0 00b 0 0 0 -
oscillator
Divide-by-2
1 0 01b 0 0 0 -
mode
Divide-by-4
1 0 10b 0 0 0 -
Divide-by-8
10-0 10-
Divide-by-16
1 0 11b 0 0 0 -
On-chip oscillator 1 0 (NOTE 2) 0 (NOTE 2) 1 -
low power dissipation
mode
-: 0 or 1
NOTES:
1. When the CM05 bit is set to 1 (main clock turned off) in low-speed mode, the mode goes to low power
dissipation mode and the CM06 bit is set to 1 (divide-by-8 mode) simultaneously.
2. The divide-by-n value can be selected the same way as in on-chip oscillator mode.
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