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M30245 Group
System Clock
Rev.2.00
Oct 16, 2006
page 41 of 264
REJ03B0005-0200
Figure 1.21.
Clock control registers 0 and 1
System clock control registers
Figure 1.21 shows the system clock control registers 0 and 1.
Bit Symbol
Bit Name
Function
R W
Symbol
CM0
Address
0006
16
When reset
48
16
System clock control register 0 (Note 1)
b7
b5
b6
b4
b3
b2
b1
b0
CM02
CM03
CM04
CM05
CM06
CM07
Reserved bit
WAIT peripheral function
clock stop bit
XCIN-XCOUT drive capacity
select bit (Note 2)
Port Xc select bit
Main clock (XIN-XOUT)
stop bit (Note 3, 4, 5)
Main clock division select
bit 0 (Note 6)
System clock select bit
(Note 7)
Always set to "0"
0 : Do not stop in wait mode
1 : Stop in wait mode (Note 8)
0 : LOW
1 : HIGH
0 : I/O port
1 : XCIN-XCOUT generation
0 : On
1 : Off
0 : CM16 and CM17 valid
1 : Divide-by-8 mode
0 : XIN, XOUT
1 : XCIN, XCOUT
O O
Note 1: Set bit 0 of the protect register (address 000A
16) to "1" before writing to this register.
Note 2: Changes to "1" when changing to Stop mode and Reset.
Note 3: When entering power saving mode, main clock is stopped using this bit. When returning from
stop mode and operating in XIN, set this bit to "0". When main clock oscillation is operating
by itself, set system clock select bit (CM07) to "1" before setting this bit to "1".
Note 4: When inputting external clock, only clock oscillation buffer is stopped and clock input is
acceptable.
Note 5: If this bit is set to "1", XOUT becomes "H". The built-in feedback resistor remains connected,
so XIN becomes pulled up to XOUT ("H") using the feedback resistor.
Note 6: This bit changes to "1" when changing from high-speed/medium mode to stop mode and at
reset. When shifting from low-speed/low power dissipation mode to stop mode, the value
before stop mode is retained.
Note 7: Set Port Xc select bit (CM04) to "1" and stabilize the sub clock oscillating before setting to
this bit from "0" to "1". Do not write to both bits at the same time. Also, set the main clock
stop bit (CM05) to "0" and stabilize the main clock oscillating before setting this bit from '1"
to "0".
Note 8: fc32 is not included. Do not set to "1" when using low-speed or low power dissipation mode.
Bit Symbol
Bit Name
Function
R W
O O
Symbol
CM1
Address
0007
16
When reset
20
16
System clock control register 1 (Note 1)
b7
b5
b6
b4
b3
b2
b1
b0
CM10
Reserved bit
CM15
CM16
CM17
All clock stop control bit
(Note 4)
0 : Clock on
1 : All clocks off (stop mode)
Always set to "0"
0 : LOW
1 : HIGH
b7 b6
0 0 : No division mode
0 1 : Divide-by-2 mode
1 0 : Divide-by-4 mode
1 1 : Divide-by-16 mode
O O
XIN-XOUT drive capacity
select bit (Note 2)
Main clock division select
bit 1 (Note 3)
0
Note 1: Set bit "0" of the protect register (address 000A
16) to "1" before writing to this register.
Note 2: This bit changes to "1" when shifting from high-speed/medium speed mode to stop mode an
at reset. When shifting from low-speed/low power dissipation mode to stop mode, the value
before stop mode is retained.
Note 3: Can be selected when bit 6 of the system clock control register 0 (address 0006
16) is "0". If
"1", divide mode is fixed at 8.
Note 4: If this bit is set to "1", XOUT becomes "H" and the built-in feedback resistoris cut off.
XCIN and XcOUT become high impedance state.
0 0