High Speed I/O
Pulse Width Modulation (PWM) Functions
On units that support the PWM, two dedicated outputs are available that can be configured for one of four modes of
operation. Those modes are Normal, PWM, HSC (count = PV) and Stepper.
Normal - When either Q1 or Q2 is configured for Normal operation, the digital output registers %Q1 and %Q2
drives that respective output.
Duty Cycle - The Duty Cycle is a 32-bit value from 0 to 32,000 indicating the relative duty cycle of the output. For
example, a value of 8000 would indicate a 25% duty cycle, a value of 16,000 would indicate a 50% duty cycle. Zero
(0) turns the output off, 32,000 turns the output on.
Frequency - The Frequency is a 32-bit value indicating the output frequency in Hertz. One over the frequency is the
period.
At controller power-up or during a download, the PWM output is maintained at zero until both the Frequency and the
Duty cycle are loaded with non-zero values.
When the controller is placed in stop mode, the state of the PWM outputs is dependent on the PWM State on Con-
troller Stop configuration. This configuration allows for either hold-last-state or specific frequency and duty cycle
counts.
Specifying zero for either the period or duty causes the PWM output to remain low during stop mode.
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