MC68HC08AS32 Datasheet, PDF (246/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

NOTE:
Before changing a channel function by writing to the MSxB or MSxA bit, set the
TSTOP and TRST bits in the TIM status and control register (TSC).
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/TCHx or pin PTFx/TCHx 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, or output compare
mode is enabled. Table 15-2 shows how ELSxB and ELSxA work. Reset clears
the ELSxB and ELSxA bits.
Table 15-2. Mode, Edge, and Level Selection
MSxB–MSxA
X0
X1
00
00
00
01
01
01
1X
1X
1X
ELSxB–ELSxA
00
00
01
10
11
01
10
11
01
10
11
Mode
Output
preset
Input
capture
Output
compare
or PWM
Buffered
output
compare
or buffered
PWM
Configuration
Pin under port control;
Initialize timer
Output level high
Pin under port control;
Initialize timer
Output level low
Capture on rising edge only
Capture on falling edge only
Capture on rising or falling edge
Toggle output on compare
Clear output on compare
Set output on compare
Toggle output on compare
Clear output on compare
Set output on compare
NOTE:
Before enabling a TIM channel register for input capture operation, make sure that
the PTEx/TCHx pin or PTFx/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.
Data Sheet
246
MC68HC08AS32 — Rev. 4.1
Freescale Semiconductor