Freescale Semiconductor, Inc.
Capture/Compare Timer
Timer Operation
8.3.2 Output Compare
The output compare function can generate an output signal when the
16-bit counter reaches a selected value. Software writes the selected
value into the output compare registers. On every fourth internal clock
cycle the output compare circuitry compares the value of the counter to
the value written in the output compare registers. When a match occurs,
the timer transfers the programmable output level bit (OLVL) from the
timer control register to the output compare pin (TCMP).
Software can use the output compare register to measure time periods,
to generate timing delays, or to generate a pulse of specific duration or
a pulse train of specific frequency and duty cycle on the TCMP pin.
Figure 8-4 shows the logic of the output compare function.
15
0
COUNTER LOW BYTE
COUNTER HIGH BYTE
PIN
CONTROL
LOGIC
16-BIT COMPARATOR
TCMP
8
0
7
15
OUTPUT COMPARE REGISTER HIGH
$0016
OUTPUT COMPARE REGISTER LOW
$0017
TIMER
INTERRUPT
REQUEST
TIMER STATUS REGISTER
$0013
TIMER STATUS REGISTER
$0012
Figure 8-4. Output Compare Operation
MC68HC705C8A — Rev. 3
MOTOROLA
Technical Data
Capture/Compare Timer
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