MC68HC08AZ16 Datasheet, PDF (251/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Timer Interface Module A (TIMA)
Input capture
With the input capture function, the TIMA can capture the time at which
an external event occurs. When an active edge occurs on the pin of an
input capture channel, the TIMA latches the contents of the TIMA
counter into the TIMA channel registers, TACHxH:TACHxL. The polarity
of the active edge is programmable. Input captures can generate
TIM CPU interrupt requests.
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 TIM CPU interrupt requests.
Unbuffered output
compare
Any output compare channel can generate unbuffered output compare
pulses as described in Output compare on page 250. 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,
using a TIMA overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMA may
pass the new value before it is written.
Use the following methods to synchronize unbuffered changes in the
output compare value on channel x:
• When changing to a smaller value, enable channel x output
compare interrupts and write the new value in the output compare
interrupt routine. The output compare interrupt occurs at the end
of the current output compare pulse. The interrupt routine has until
the end of the counter overflow period to write the new value.
MC68HC08AZ32
250
Timer Interface Module A (TIMA)
6-tima
MOTOROLA