
I/O Registers
MC68HC08KH12A Data Sheet, Rev. 1.1
Freescale Semiconductor
123
NOTE
Before enabling a TIM channel register for input capture operation, make
sure that the PTEx/TCHx pin is stable for at least two bus clocks.
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIM counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIM counter overflow
0 = Channel x pin does not toggle on TIM counter overflow
NOTE
When TOVx is set, a TIM counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at logic one, setting the CHxMAX bit forces the duty cycle of buffered and
unbuffered PWM signals to 100%. As
Figure 11-8
shows, the CHxMAX bit takes effect in the cycle after
it is set or cleared. The output stays at the 100% duty cycle level until the cycle after CHxMAX is
cleared.
Figure 11-8. CHxMAX Latency
Table 11-3. Mode, Edge, and Level Selection
MSxB
MSxA
ELSxB
ELSxA
Mode
Configuration
X
0
0
0
Output Preset
Pin under Port Control;
Initial Output Level High
X
1
0
0
Pin under Port Control;
Initial Output Level Low
0
0
0
1
Input Capture
Capture on Rising Edge Only
0
0
1
0
Capture on Falling Edge Only
0
0
1
1
Capture on Rising or Falling Edge
0
1
0
1
Output Compare or PWM
Toggle Output on Compare
0
1
1
0
Clear Output on Compare
0
1
1
1
Set Output on Compare
1
X
0
1
Buffered Output Compare
or
Buffered PWM
Toggle Output on Compare
1
X
1
0
Clear Output on Compare
1
X
1
1
Set Output on Compare
OUTPUT
COMPARE
OVERFLOW
PTEx/TCHx
PERIOD
CHxMAX
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE