Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
220 Timer Interface A (TIMA) MOTOROLA
Timer Interface A (TIMA)
When ELSxB:A = 00, this read/write bit selects the initial output level
of the TCHxA pin once PWM, input capture, or output compare
operation is enabled. See Table 11-2. Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE: Before changing a channel function by writ ing to the MS xB or MS xA bit,
set the TSTOP and TRST bits in the TIMA stat us 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, and pin PTEx/TCHxA is available as a genera l-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 11-2 shows how ELSxB
and ELSxA work. Reset clears the ELSxB and ELSxA bits.
Table 11-2. Mode, Edge, and Level Selection
MSxB:MSxA ELSxB:ELSxA Mode Configuration
X0 00 Output preset Pin under port control; initialize timer output level high
X1 00 Pin under port control; initialize timer output lev el low
00 01
Input capture
Capture on rising edge only
00 10 Capture on falling edge only
00 11 Capture on rising or falling edge
01 01 Output
compare
or PWM
Toggle output on compare
01 10 Clear output on compare
01 11 Set output on compare
1X 01 Buffered
output compare
or buffered PWM
Toggle output on compare
1X 10 Clear output on compare
1X 11 Set output on compare