MC68HC08AZ32A Datasheet, PDF (251/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

I/O Registers
Setting MS0B disables the channel 1 status and control register and reverts TACH1 pin to
general-purpose I/O.
Setting MS2B disables the channel 3 status and control register and reverts TACH3 pin to
general-purpose I/O.
Setting MS4B disables the channel 5 status and control register and reverts TACH5 pin to
general-purpose I/O.
Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture operation or unbuffered output
compare/PWM operation. See Table 17-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level of the TACHx pin once PWM,
output compare mode or input capture mode is enabled. See Table 17-2. Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MSxB or MSxA bit, set
the TSTOP and TRST bits in the TIMA status and control register (TASC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port E or port F and pin
PTEx/TACHx or pin PTFx/TACHx is available as a general-purpose I/O pin. However, channel x is at
a state determined by these bits and becomes transparent to the respective pin when PWM, input
capture mode or output compare operation mode is enabled. Table 17-2 shows how ELSxB and
ELSxA work. Reset clears the ELSxB and ELSxA bits.
NOTE
Before enabling a TIMA channel register for input capture operation, make
sure that the PTEx/TACHx pin or PTFx/TACHx 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 TIMA 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 TIMA counter overflow.
0 = Channel x pin does not toggle on TIMA counter overflow.
NOTE
When TOVx is set, a TIMA counter overflow takes precedence over a
channel x output compare if both occur at the same time.
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
251