ZBasic System Library
254
ZBasic Microcontrollers
Type
Subroutine
Invocation
PWM8(channel, dutyCycle)
PWM8(channel, dutyCycle, status)
Parameter
Method
Type
Description
channel
ByVal
Byte
The channel to use for 8-bit PWM generation.
dutyCycle
ByVal
Single or integral
The desired duty cycle.
status
ByRef
Boolean
The variable to receive the status value.
Discussion
This subroutine begins or modifies the generation of an 8-bit PWM signal on the specified channel. The
channel must have been previously prepared for PWM generation by calling OpenPWM8(). Eight-bit
PWM generation is performed using one of the CPU’s 8-bit timers, the number of which varies depending
on the ZBasic device. See the Resource Usage sub-section 8-Bit PWM Timers for details of the available
channels and the corresponding timer and output pin used. Note that ZBasic devices based on ATxmega
processors don’t have any 8-bit timers so 8-bit PWM is not supported on those devices. The table below
indicates the output pin for each PWM supported channel.
The dutyCycle parameter specifies the desired duty cycle of the generated signal, expressing the
percentage of time that the PWM signal will be at the logic 1 state. If the supplied parameter is of type
Single, the value is in percent with a resolution of 0.01%. If the supplied parameter is integral, the units
are percent, i.e., the value 100 means 100%. Specifying a Single value that is negative or any value
greater than 100 will have an undefined effect.
The status parameter, if supplied, receives a value to indicate success or failure of the call.
If this subroutine is called without a preceding call to OpenPWM8() to prepare the timer, the call will have
no effect. This subroutine may be called multiple times to effect changes to the PWM signal’s duty cycle
while the signal is being generated. The change in duty cycle is synchronized so that it takes effect at the
beginning of the next PWM pulse.
Example
Call OpenPWM8(1, 50.0, zxFastPWM) ' prepare for 50Hz Fast PWM
Call PWM8(1, 50.0) ' generate PWM with 50% duty cycle
Compatibility
This subroutine is not available in BasicX compatibility mode nor is it available on ATxmega-based
ZBasic devices.
See Also
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