TIME PROCESSOR UNIT
MC68332
7-10
USER’S MANUAL
specified number of transitions, ceasing channel activity until reinitialization. After
each transition or specified number of transitions, the channel can generate a link to
other channels.
7.5.3 Queued Output Match (QOM)
QOM can generate single or multiple output match events from a table of offsets in pa-
rameter RAM. Loop modes allow complex pulse trains to be generated once, a spec-
ified number of times, or continuously. The function can be triggered by a link from
another TPU channel. In addition, the reference time for the sequence of matches can
be obtained from another channel. QOM can generate pulse-width modulated wave-
forms, including waveforms with high times of 0% or 100%. QOM also allows a TPU
channel to be used as a discrete output pin.
7.5.4 Programmable Time Accumulator (PTA)
PTA accumulates a 32-bit sum of the total high time, low time, or period of an input
signal over a programmable number of periods or pulses. The accumulation can start
on a rising or falling edge. After the specified number of periods or pulses, the PTA
generates an interrupt request and optionally generates links to other channels.
From 1 to 255 period measurements can be made and summed with the previous
measurement(s) before the TPU interrupts the CPU, providing instantaneous or aver-
age frequency measurement capability, and the latest complete accumulation (over
the programmed number of periods).
7.5.5 Multichannel Pulse-Width Modulation (MCPWM)
MCPWM generates pulse-width modulated outputs with full 0% to 100% duty cycle
range independent of other TPU activity. This capability requires two TPU channels
plus an external gate for one PWM channel. (A simple one-channel PWM capability is
supported by the QOM function.)
Multiple PWMs generated by MCPWM have two types of high time alignment: edge
aligned and center aligned. Edge aligned mode uses n + 1 TPU channels for n PWMs;
center aligned mode uses 2n + 1 channels. Center aligned mode allows a user defined
“dead time” to be specified so that two PWMs can be used to drive an H-bridge without
destructive current spikes. This feature is important for motor control applications.
7.5.6 Fast Quadrature Decode (FQD)
FQD is a position feedback function for motor control. It decodes the two signals from
a slotted encoder to provide the CPU with a 16-bit free running position counter. FQD
incorporates a “speed switch” which disables one of the channels at high speed, al-
lowing faster signals to be decoded. A time stamp is provided on every counter update
to allow position interpolation and better velocity determination at low speed or when
low resolution encoders are used. The third index channel provided by some encoders
is handled by the ITC function.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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