s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 104

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Oscillator Mode (OSC)
OSCOPT1:OSCOPT0 — OSC Option Bits
ICFS1:ICFS0 — Internal Clock Frequency Select Bits
ECFS1:ECFS0 — External Crystal Frequency Select Bits
ECGON — External Clock Generator On Bit
104
These read/write bits allow the user to change the clock source for the MCU. The default reset
condition has the bus clock being derived from the internal oscillator. See
Clock Switching
These read/write bits enable the frequency to be increased for applications requiring a faster bus clock
when running off the internal oscillator. The WAIT instruction has no effect on the oscillator logic.
BUSCLKX2 and BUSCLKX4 continue to drive to the SIM module.
These read/write bits enable the specific amplifier for the crystal frequency range. Refer to oscillator
characteristics table in the Electricals section for information on maximum external clock frequency
versus supply voltage.
This read/write bit enables the OSC1 pin as the clock input to the MCU, so that the switching process
can be initiated. This bit is cleared by reset. This bit is ignored in monitor mode with the internal
oscillator bypassed.
1 = External clock enabled
0 = External clock disabled
Reset:
Read:
Write:
OSCOPT1
ECFS1
ICFS1
Figure 10-4. Oscillator Status and Control Register (OSCSC)
for information on changing clock sources.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
OSCOPT1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 7
0
= Unimplemented
OSCOPT0
OSCOPT0
ECFS0
ICFS0
6
0
0
1
0
1
0
1
0
1
0
1
0
1
ICFS1
4.0 MHz — default reset condition
8.0 MHz
12.8 MHz
25.6 MHz
8 MHz – 32 MHz
1 MHz – 8 MHz
32 kHz – 100 kHz
Reserved
Internal oscillator (frequency selected using ICFSx bits)
External oscillator clock
External RC
External crystal (range selected using ECFSx bits)
5
0
ICFS0
4
0
External Crystal Frequency
Internal Clock Frequency
Oscillator Modes
ECFS1
3
0
ECFS0
2
0
ECGON
10.3.2.2 Internal to External
1
0
Freescale Semiconductor
ECGST
Bit 0
0