mc68hc908sr12 Freescale Semiconductor, Inc, mc68hc908sr12 Datasheet - Page 105

• Manufacturer Part Number: mc68hc908sr12
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

7.3.2 TBM Reference Clock Selection
7.4 Internal Oscillator
MC68HC908SR12•MC68HC08SR12 — Rev. 5.0
Freescale Semiconductor
NOTE:
Address:
The timebase module reference clock (OSCCLK) is selected by
configuring two bits in the CONFIG2 register, at $001D. See
Configuration Register 2
The RCCLK or XCLK is only available if that clock is selected as the
CGM reference clock, whereas the ICLK is always available.
The internal oscillator clock (ICLK) is a free running 24kHz clock that
requires no external components. It can be selected as the CGMXCLK
for the CGM and MCU sub-systems; and the OSCCLK clock for the
TBM. The ICLK is also the reference clock input to the computer
operating properly (COP) module.
Due to the simplicity of the internal oscillator, it does not have the
accuracy and stability of the RC oscillator or the x-tal oscillator.
Therefore, the ICLK is not suitable where an accurate bus clock is
required and it should not be used as the CGMRCLK to the CGM PLL.
Reset:
Read: STOP_
Write:
OSCCLK1
Table 7-2. Timebase Module Reference Clock Selection
ICLKEN
$001D
Bit 7
Figure 7-3. Configuration Register 2 (CONFIG2)
0
0
1
1
0
RCLKEN
STOP_
Oscillator (OSC)
6
0
XCLKEN
STOP_
5
0
OSCCLK0
(CONFIG2).
0
1
0
1
OSCCLK1 OSCCLK0
4
0
3
0
Timebase Clock Source
Internal oscillator (ICLK)
RC oscillator (RCCLK)
X-tal oscillator (XCLK)
2
0
0
Not used
CDOEN
Internal Oscillator
Oscillator (OSC)
1
0
5.5
Data Sheet
SCIBDSRC
Bit 0
0
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