MC908AS60ACFU Datasheet, PDF (241/414 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

I/O Registers
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 TIMB 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 TIMB counter overflow.
0 = Channel x pin does not toggle on TIMB counter overflow.
NOTE
When TOVx is set, a TIMB 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 1, setting the CHxMAX bit forces the duty cycle of buffered and
unbuffered PWM signals to 100%. As Figure 20-8 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.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTEx/TCHx
CHxMAX
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 20-8. CHxMAX Latency
20.8.5 TIMB Channel Registers
These read/write registers contain the captured TIMB counter value of the input capture function or the
output compare value of the output compare function. The state of the TIMB channel registers after reset
is unknown.
In input capture mode (MSxB–MSxA = 0:0) reading the high byte of the TIMB channel x registers
(TBCHxH) inhibits input captures until the low byte (TBCHxL) is read.
In output compare mode (MSxB–MSxA ≠ 0:0) writing to the high byte of the TIMB channel x registers
(TBCHxH) inhibits output compares and the CHxF bit until the low byte (TBCHxL) is written.
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
Freescale Semiconductor
241