Datasheet

Mask Option Register (MOR)
MC68HC908AP Family Data Sheet, Rev. 4
Freescale Semiconductor 53
SCIBDSRC — SCI Baud Rate Clock Source
SCIBDSRC selects the clock source used for the standard SCI module (non-infrared SCI). The setting
of this bit affects the frequency at which the SCI operates.
1 = Internal data bus clock, f
BUS
, is used as clock source for SCI
0 = Oscillator clock, CGMXCLK, is used as clock source for SCI
3.5 Mask Option Register (MOR)
The mask option register (MOR) is used for selecting one of the three clock options for the MCU. The
MOR is a byte located in FLASH memory, and is written to by a FLASH programming routine.
OSCSEL1, OSCSEL0 — Oscillator Selection Bits
OSCSEL1 and OSCSEL0 select which oscillator is used for the MCU CGMXCLK clock. The erase
state of these two bits is logic 1. These bits are unaffected by reset. (See Table 3-1).
Bits 5–0 — Should be left as 1’s
NOTE
The internal oscillator is a free running oscillator and is available after each
POR or reset. It is turned-off in stop mode by setting the STOP_ICLKDIS
bit in CONFIG2.
Address: $FFCF
Bit 7654321Bit 0
Read:
OSCSEL1 OSCSEL0 RRRRRR
Write:
Reset: Unaffected by reset
Erased:11111111
R = Reserved
Figure 3-4. Mask Option Register (MOR)
Table 3-1. CGMXCLK Clock Selection
OSCSEL1 OSCSEL0 CGMXCLK OSC2 pin Comments
00——
Not used
0 1 ICLK
f
BUS
Internal oscillator generates the CGMXCLK.
1 0 RCCLK
f
BUS
RC oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
1 1 X-TAL
Inverting
output of XTAL
X-tal oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.