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REV.-A
<PRC>
The method by which PRC is carried out by the control circuit may be explained as follows. An internal
trigger pulse used to control motor linkage is created in sync with the positive-going edge of the encoder
A phase signal.
This trigger pulse is used to generate a one-shot signal that is in line with the set speed. The following
positive-going edge of the encoder A phase signal is then used to compare the time lapse from the
one-shot pulse against the positive going edge.
If the positive-going edge of the encoder A phase signal is later than the one-shot time lapse, then the
motor will be energized for the single cycle time of the next encoder A phase signal. If, on the other
hand, the positive-going edge is earlier than the one-shot time lapse, energizing will not occur. Thus,
the circuit maintains the desired set speed by causing motor energizing to be switched ON and OFF
in sync with the encoder A phase signal.
Figure 2-51 illustrates the PRC energizing signal.
OFF
ON
ON
ON
Setting Speed
I
:<
'>I
,
I
Internal
Speed
Signal
Motor
Drive
Signal
Encoder A
Phase
Differential
Signal
Figure 2-51. PRC (Accelerated speed)
Accelerated, normal, and reduced speed control are made available based on the writing of the set
speed into the internal register of the gate array.
2-47
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