R01UH0092EJ0110 Rev.1.10
Page 89 of 807
Jul 31, 2012
M16C/64C Group
8. Clock Generator
8.2.3
System Clock Control Register 1 (CM1)
Rewrite the CM1 register after setting the PRC0 bit in the PRCR register to 1 (write enabled).
See Table 9.3 “Clock-Related Bit Setting and Modes” to select a clock and a mode.
CM10 (All clock stop control bit) (b0)
When the CM11 bit is 1 (PLL clock), or the CM20 bit in the CM2 register is 1 (oscillator stop/restart
detect function enabled), do not set the CM10 bit to 1.
In the following cases, this bit remains unchanged even when written to (The MCU does not enter stop
mode).
•
The PM21 bit in the PM2 register is 1 (clock change disabled).
•
The CSPRO bit in the CSPR register is 1 (watchdog timer count source protection mode enabled).
•
The PLC07 bit in the PLC0 register is 1 (PLL on).
•
A low is input to the
NMI
pin.
CM11 (System clock select bit) (b1)
The CM11 bit is valid when the CM21 bit in the CM2 register is set to 0 (main clock or PLL clock).
The CPU clock source and the peripheral function clock f1 can be selected by the CM11 bit when the
CM07 bit is 0 (main clock, PLL clock, or on-chip oscillator clock used as CPU clock). The peripheral
function clock f1 can be selected by the CM11 bit when the CM07 bit is 1 (sub clock used as CPU
clock).
When the PM21 bit in the PM2 register is 1 (clock change disabled), the CM11 bit remains unchanged
even when written to.
b7
0
b6 b5 b4
b1
b2
b3
System Clock Control Register 1
Symbol
CM1
Address
0007h
Bit Symbol
Bit Name
RW
CM10
Reset Value
0010 0000b
b0
Function
All clock stop control bit
—
(b2)
CM14
Reserved bit
0 : Clock on
1 : All clocks off (stop mode)
CM15
Set to 0
CM16
0 : 125 kHz on-chip oscillator on
1 : 125 kHz on-chip oscillator off
RW
0 : Low
1 : High
125 kHz on-chip oscillator stop
bit
XIN-XOUT drive capacity
select bit
RW
RW
RW
RW
CM11
System clock select bit 1
0 : Main clock
1 : PLL clock
RW
CM17
Main clock division select bit 1
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
CM13
XIN-XOUT feedback resistor
select bit
0 : Internal feedback resistor connected
1 : Internal feedback resistor not connected
RW
Содержание M16C Series
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