
Rev.2.10 Apr 14, 2006 page 59 of 378
REJ09B0124-0210
M16C/6N Group (M16C/6NK, M16C/6NM) 8. Clock Generation Circuit
Figure 8.3 CM1 Register
RW
RW
RW
RW
RW
RW
RW
Bit Name FunctionBit Symbol
CM10
CM15
CM16
CM17
CM11
-
(b4-b2)
All clock stop control
bit
(2) (3)
XIN-XOUT drive capacity
select bit
(6)
Reserved bits
Main clock division
select bits 1
(7)
System clock select bit 1
(4)
0 : Clock on
1 : All clocks off (stop mode)
0 : LOW
1 : HIGH
Set to 0
0 0 : No division mode
0 1 : Divide-by-2 mode
1 0 : Divide-by-4 mode
1 1 : Divide-by-16 mode
b7 b6
0 : Main clock
1 : PLL clock
(5)
Symbol Address After Reset
CM1 0007h 00100000b
System Clock Control Register 1
(1)
000
b7 b6 b5 b4 b3 b2 b1 b0
NOTES:
1. Rewrite this register after setting the PRC0 bit in the PRCR register to 1 (write enabled)
2. If the CM10 bit is 1 (stop mode), XOUT is held "H" and the on-chip feedback resistor is disconnected.
Pins XCIN and XCOUT are in high-impedance state. When the CM11 bit is set to 1 (PLL clock), or the CM20
bit in the CM2 register is set to 1 (oscillation stop, re-oscillation detection function enabled), do not set the
CM10 bit to 1.
3. When the PM22 bit in the PM2 register is set to 1 (on-chip oscillator clock is selected as watchdog timer
count source), this bit remains unchanged even if writing to the CM10 bit.
4. This bit is valid when the CM07 bit is 0 and the CM21 bit is 0.
5. After setting the PLC07 bit in the PLC0 register to 1 (PLL operation), wait tsu(PLL) elapses before setting
the CM11 bit to 1 (PLL clock).
6. When entering stop mode from high-speed or medium-speed mode, or when the CM05 bit is set to 1 (main
clock stops) in low-speed mode, the CM15 bit is set to 1 (drive capability high).
7. This bit is valid when the CM06 bit is 0 (bits CM16 and CM17 enabled).
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