Datasheet

Oscillator (OSC)
MC68HC908AP Family Data Sheet, Rev. 4
72 Freescale Semiconductor
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 7654321Bit 0
Read:
OSCSEL1 OSCSEL0 RRRRRR
Write:
Reset: Unaffected by reset
Erased:11111111
R = Reserved
Figure 5-2. Mask Option Register (MOR)
X-TAL OSCILLATOR RC OSCILLATOR INTERNAL OSCILLATOR
MUX
OSC1 OSC2
BUS CLOCK
From SIM
MUX
XCLK
RCCLK
ICLK
OSCCLK0
OSCCLK1
OSCSEL0
OSCSEL1
OSCCLK
To TBM
CGMXCLK CGMRCLK
To CGM and others
MOR CONFIG2
To CGM PLL
XRCIXRCI
To SIM
(and COP)