MC68HC08AZ60A Datasheet, PDF (409/480 Pages) Motorola, Inc – Microcontrollers

Timer Interface Module A (TIMA)
Functional Description
captured. To measure a pulse width, two alternate polarity edges are
captured. Software should track the overflows at the 16-bit module
counter to extend its range.
Another use for the input capture function is to establish a time
reference. In this case, an input capture function is used in conjunction
with an output compare function. For example, to activate an output
signal a specified number of clock cycles after detecting an input event
(edge), use the input capture function to record the time at which the
edge occurred. A number corresponding to the desired delay is added to
this captured value and stored to an output compare register (see TIMA
Channel Registers on page 429). Because both input captures and
output compares are referenced to the same 16-bit modulo counter, the
delay can be controlled to the resolution of the counter independent of
software latencies.
Reset does not affect the contents of the TIMA channel register
(TACHxH–TACHxL).
23.4.3 Output Compare
With the output compare function, the TIMA can generate a periodic
pulse with a programmable polarity, duration and frequency. When the
counter reaches the value in the registers of an output compare channel,
the TIMA can set, clear or toggle the channel pin. Output compares can
generate TIMA CPU interrupt requests.
23.4.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare
pulses as described in Output Compare on page 409. The pulses are
unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change an
output compare value could cause incorrect operation for up to two
counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new
value prevents any compare during that counter overflow period. Also,
MC68HC08AZ60A — Rev 0.0
MOTOROLA
Timer Interface Module A (TIMA)
Advance Information
409