Oscillator (OSC)
To CGM and others To CGM PLL
CGMXCLK CGMRCLK
To TBM
OSCCLK
MOR
CONFIG2
OSCCLK1
OSCCLK0
OSCSEL1
OSCSEL0
MUX
MUX
X
RC
I
X
RC
I
To SIM
(and COP)
XCLK
ICLK
RCCLK
X-TAL OSCILLATOR
RC OSCILLATOR
INTERNAL OSCILLATOR
BUS CLOCK
From SIM
OSC1
OSC2
Figure 5-1. Oscillator Module Block Diagram
5.2.1 CGM Reference Clock Selection
The clock generator module (CGM) reference clock (CGMXCLK) is the reference clock input to the MCU.
It is selected by programming two bits in a FLASH memory location; the mask option register (MOR), at
$FFCF. See 3.5 Mask Option Register (MOR).
Address: $FFCF
Bit 7
6
5
4
3
2
1
Bit 0
R
Read:
Write:
OSCSEL1 OSCSEL0
R
R
R
R
R
Reset:
Erased:
Unaffected by reset
1
1
1
1
1
1
1
1
R
= Reserved
Figure 5-2. Mask Option Register (MOR)
MC68HC908AP Family Data Sheet, Rev. 4
72
Freescale Semiconductor
FREESCALE [ Freescale ]
