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M
1
6
C
2 /
6
A
G
o r
u
p
(
M
1
Oscillation stop detection register (1)
b7
b6
b5
b4
b3
0 0
NOTES:
1. Write to this register after setting the PRC0 bit in the PRCR register to "1" (write enable).
2. When the CM20 bit is set to "1" (oscillation stop, re-oscillation detection function enabled), the CM27 bit is set to
"1"(oscillation stop, re-oscillation detection interrupt), and the CPU clock source is the main clock, the CM21 bit
isautomatically set to "1" (on-chip oscillator clock) if the main clock stop is detected.
3. If the CM20 bit is set to "1" and the CM23 bit is set to "1" (main clock not oscillating), do not set the CM21 bit to "0".
4. This flag is set to "1" when the main clock is detected to have stopped or when the main clock is detected to
haverestarted oscillating. When this flag changes state from "0" to "1", an oscillation stop, reoscillation detection interrupt
isgenerated. Use this flag in an interrupt routine to discriminate the causes of interrupts between theoscillation
stop,reoscillation detection interrupts and the watchdog timer interrupt. The flag is cleared to "0" by writing a "0" in
aprogram. (Writing a "1" has no effect. Nor is it cleared to "0" by an oscillation stop or an oscillation restart
detectiointerrupt request acknowledged.) If when the CM22 bit is set to "1" an oscillation stop or an oscillation restart is
detected, no oscillation stop, reoscillation detection interrupts are generated.
5. Read the CM23 bit in an oscillation stop, re-oscillation detection interrupt handling routine to determine the main
clockstatus.
6. Effective when the CM07 bit in the CM0 register is set to "0".
7. When the PM21 bit in the PM2 register is "1" (clock modification disabled), writing to the CM20 bit has no effect.
8. When the CM20 bit is set to "1" (oscillation stop, re-oscillation detection function enabled), the CM27 bit is set to "1"
(oscillation stop, re-oscillation detection interrupt), and the CM11 bit is set to "1" (the CPU clock source is PLL clock), the
CM21 bit remains unchanged even when main clock stop is detected. If the CM22 bit is set to "0" under these conditions,
oscillation stop, re-oscillation detection interrupt occur at main clock stop detection; it is, therefore, necessary to set the
CM21 bit to "1" (on-chip oscillator clock) inside the interrupt routine.
9. Set the CM20 bit to "0" (disable) before entering stop mode. After exiting stop mode, set the CM20 bit back to "1"
(enable).
10. Set the CM20 bit to "0" (disable) before setting the CM05 bit in the CM0 register.
11. The CM20, CM21 and CM27 bits do not change at oscillation stop detection reset.
12. When the CM21 bit is set to "0" (on-chip oscillator turned off) and the CM05 bit is set to "1" (main clock turned off), the
CM06 bit is fixed to "1" (divide-by-8 mode) and the CM15 bit is fixed to "1" (drive capability High).
Figure 7.5. CM2 Register
R
e
. v
2
0 .
0
F
e
b
1 .
, 5
2
0
0
7
R
E
J
0
9
B
0
2
0
2
0 -
2
0
0
6
C
2 /
6
, A
M
1
6
C
2 /
6
, B
M
1
b2
b1
b0
Symbol
CM2
Bit symbol
Oscillation stop, re-
CM20
oscillation detection bit
(7, 9, 10, 11)
System clock select bit 2
CM21
(2, 3, 6, 8, 11, 12 )
Oscillation stop, re-
CM22
oscillation detection flag
(4)
X
IN
CM23
(5)
Reserved bit
(b5-b4)
Nothing is assigned. When write, set to "0". When read, its
(b6)
content is indeterminate.
Operation select bit
CM27
(when an oscillation stop,
re-oscillation is detected)
(11)
page 42
f o
3
2
9
6
C
2 /
6
) T
Address
000C
16
Bit name
0: Oscillation stop, re-oscillation
detection function disabled
1: Oscillation stop, re-oscillation
detection function enabled
0: Main clock or PLL clock
1: On-chip oscillator clock
(On-chip oscillator oscillating)
0: Main clock stop or re-oscillation
not detected
1: Main clock stop or re-oscillation
detected
0: Main clock oscillating
monitor flag
1: Main clock not oscillating
Must set to "0"
0: Oscillation stop detection reset
1: Oscillation stop, re-oscillation
detection interrupt
7. Clock Generation Circuit
After reset
0X000010
(11)
2
Function
RW
RW
RW
RW
RO
RW
RW
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