Datasheet

Clock Functions
Technical Data MC68HC912D60A — Rev. 3.1
164 Clock Functions Freescale Semiconductor
the transition, the clock select output will be held low and all CPU activity
will cease until the transition is complete.
The Module Clock Select bit MCS determines the clock used by the ECT
module and the baud rate generators of the SCIs. In limp-home mode,
the output of MCS is forced to 0, but the MCS bit reads the latched value.
It allows normal operation of the serial and timer subsystems at a fixed
reference frequency while allowing the CPU to operate at a higher,
variable frequency.
Figure 11-7. Clock Chain for SCI0, SCI1, RTI, COP
XCLK
SC0BD
MODULUS DIVIDER:
÷ 1, 2, 3, 4, 5, 6,...,8190, 8191
SCI0
RECEIVE
BAUD RATE (16x)
SCI0
TRANSMIT
BAUD RATE (1x)
BITS: RTR2, RTR1, RTR0
TO RTI
BITS: CR2, CR1, CR0
TO COP
÷ 16
SCI1
RECEIVE
BAUD RATE (16x)
SCI1
TRANSMIT
BAUD RATE (1x)
÷ 16
0:0:0
0:0:1
0:1:0
0:1:1
1:0:0
1:0:1
1:1:0
1:1:1
÷ 2
÷ 2
÷ 2
÷ 2
÷ 2
÷ 2
0:0:0
0:0:1
0:1:0
0:1:1
1:0:0
1:0:1
1:1:0
1:1:1
÷ 4
÷ 4
÷ 4
÷ 2
÷ 4
÷ 2
÷4
REGISTER: COPCTL
REGISTER: RTICTL
SC1BD
MODULUS DIVIDER:
÷ 1, 2, 3, 4, 5, 6,...,8190, 8191
REGISTER: RTICTL
BIT:RTBYP
÷ 2048
MCLK