MC68336/376
TIME PROCESSOR UNIT
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
11-7
Refer to TPU programming note Input Capture/Input Transition Counter (ITC) TPU
Function (TPUPN16/D) for more information.
11.4.3 Output Compare (OC)
The output compare function generates a rising edge, a falling edge, or a toggle of the
previous edge in one of three ways:
1. Immediately upon CPU32 initiation, thereby generating a pulse with a length
equal to a programmable delay time.
2. At a programmable delay time from a user-specified time.
3. As a continuous square wave. Upon receiving a link from a channel, OC refer-
ences, without CPU32 interaction, a specifiable period and calculates an offset:
where “RATIO” is a parameter supplied by the user.
This algorithm generates a 50% duty-cycle continuous square wave with each high/
low time equal to the calculated offset. Due to offset calculation, there is an initial link
time before continuous pulse generation begins.
Refer to TPU programming note Output Compare (OC) TPU Function (TPUPN12/
D) for more information.
11.4.4 Pulse-Width Modulation (PWM)
The TPU can generate a pulse-width modulated waveform with any duty cycle from
zero to 100% (within the resolution and latency capability of the TPU). To define the
PWM, the CPU32 provides one parameter that indicates the period and another
parameter that indicates the high time. Updates to one or both of these parameters
can direct the waveform change to take effect immediately, or coherently beginning at
the next low-to-high transition of the pin.
Refer to TPU programming note Pulse-Width Modulation (PWM) TPU Function
(TPUPN17/D) for more information.
11.4.5 Synchronized Pulse-Width Modulation (SPWM)
The TPU generates a PWM waveform in which the CPU32 can change the period and/
or high time at any time. When synchronized to a time function on a second channel,
the synchronized PWM low-to-high transitions have a time relationship to transitions
on the second channel.
Refer to TPU programming note Synchronized Pulse-Width Modulation (SPWM)
TPU Function (TPUPN19/D) for more information.
11.4.6 Period Measurement with Additional Transition Detect (PMA)
This function and the following function are used primarily in toothed-wheel speed-
sensing applications, such as monitoring rotational speed of an engine. The period
OFFSET
PERIOD RATIO
=