Mask Option Register (MOR)
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
, is used as clock source for SCI
BUS
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.
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 3-4. Mask Option Register (MOR)
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
Table 3-1. CGMXCLK Clock Selection
OSCSEL1
OSCSEL0
CGMXCLK
—
OSC2 pin
—
Comments
0
0
0
1
Not used
fBUS
ICLK
Internal oscillator generates the CGMXCLK.
RC oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
fBUS
1
1
0
1
RCCLK
X-TAL
X-tal oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
Inverting
output of XTAL
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.
MC68HC908AP Family Data Sheet, Rev. 4
Freescale Semiconductor
53
FREESCALE [ Freescale ]
