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ZBasic System Library
227
ZX Microcontroller Family
PWM8
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 ZX model. Note that ZX 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.
Output Pins for 8-bit PWM Channel Numbers
ZX Models
Timer
Chan 1
Chan 2
ZX-24
Timer2
25, D.7
-
ZX-40
Timer2
21, D.7
-
ZX-44
Timer2
16, D.7
-
ZX-24a, ZX-24p, ZX-24n, ZX-24r, ZX-24s
Timer2
25, D.7
12, D.6
ZX-40a, ZX-40p, ZX-40n, ZX-40r, ZX-40s
Timer2
21, D.7
20, D.6
ZX-44a, ZX-44p, ZX-44n, ZX-44r, ZX-44s
Timer2
16, D.7
15, D.6
ZX-328n, ZX-328l
Timer2
17, B.3
5, D.3
ZX-32n, ZX-32l
Timer2
15, B.3
1, D.3
ZX-1281, ZX-1281n
Timer0
17, B.7
1, G.5
ZX-1280, ZX-1280n
Timer0
26, B.7
1, G.5
ZX-24e
Timer2
13, D.7
-
ZX-24ae, ZX-24ne, ZX-24pe,
ZX-24nu, ZX-24pu, ZX-24ru, ZX-24su
Timer2
13, D.7
14, D.6
ZX-128e, ZX-128ne
Timer2
17, B.7
-
ZX-1281e, ZX-1281ne
Timer0
21, B.7
G.5
ZX-328nu
Timer2
14, B.3
6, D.3
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.
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