mc68hc908mr24 Freescale Semiconductor, Inc, mc68hc908mr24 Datasheet - Page 236

• Manufacturer Part Number: mc68hc908mr24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Timer Interface B (TIMB)
12.4.3 Output Compare
12.4.3.1 Unbuffered Output Compare
Advance Information
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measure a period, two successive edges of the same polarity are
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
TIMB Channel
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 input capture channel register
(TBCHxH–TBCHxL).
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 TIMB CPU interrupt requests.
Any output compare channel can generate unbuffered output compare
pulses as described in
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
Timer Interface B (TIMB)
Registers). Because both input captures and output
12.4.3 Output
Compare. The pulses are
MC68HC908MR24
Freescale Semiconductor
—
Rev. 4.1
12.8.5