MC68HC708MP16 Datasheet, PDF (230/398 Pages) Freescale Semiconductor, Inc – Microcontrollers

Timer Interface Module B (TIMB)
12.4.1 TIMB Counter Prescaler
The TIMB clock source can be one of the seven prescaler outputs or the
TIMB clock pin, PTE3/TCLKB. The prescaler generates seven clock
rates from the internal bus clock. The prescaler select bits, PS[2:0], in
the TIMB status and control register select the TIMB clock source.
12.4.2 Input Capture
With the input capture function, the TIMB can capture the time at which
an external event occurs. When an active edge occurs on the pin of an
input capture channel, the TIMB latches the contents of the TIMB
counter into the TIMB channel registers, TBCHxH:TBCHxL. The polarity
of the active edge is programmable. Input captures can generate
TIM CPU interrupt requests.
12.4.3 Output Compare
With the output compare function, the TIMB 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 TIMB can set, clear, or toggle the channel pin. Output compares can
generate TIM CPU interrupt requests.
12.4.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare
pulses as described in 12.4.3 Output Compare. The pulses are
unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMB channel registers.
An unsynchronized write to the TIMB 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 TIMB overflow interrupt routine to write a new, smaller output
Technical Data
230
Timer Interface Module B (TIMB)
MC68HC708MP16 — Rev. 3.1
Freescale Semiconductor