ZBasic System Library
235
ZBasic Microcontrollers
Type
Subroutine
Invocation
PulseOut(pin, duration, level)
Parameter
Method
Type
Description
pin
ByVal
Byte
The pin on which a pulse width will be generated.
duration
ByVal
int16 or Single
The width of the generated pulse.
level
ByVal
Byte
The desired pulse logic value (low = 0, high = 1).
Discussion
This routine first makes the specified pin an output. (However, for practical purposes, you should
generally make the pin an output and set it to the desired state before calling this routine.) Then it sets
the pin to the active state (as indicated by the level parameter), waits the specified time and then sets
the pin back to the inactive state. The pin will be left configured as an output.
The pulse width may be specified by a Single value with units of seconds and a resolution as shown in
the table below. Note, however, that due to processing overhead, the shortest pulse that can be
generated is approximately 200 CPU cycles (13us at 14.7MHz). Alternately, the pulse width may be
specified by an Integer or UnsignedInteger value with units as shown in the table below. Note, however,
that Register.TimerSpeed2 may be modified to adjust the I/O Timer tick rate. If this is done, the Single
value will have to be scaled proportionally.
PulseOut Resolution
Target
I/O Scaling
Resolution
ZX devices running at 14.7456MHz
True
False
1.085 µS
0.542 µS
all other targets
n/a
1/F_TS2
If the output pin is specified as zero, this routine does not generate a pulse but will delay for
approximately the specified period of time. This may be useful for generating a delay with better
precision than can be obtained by using Delay() or Sleep(). Moreover, generating a delay in this
manner does not cause the task to lose control.
Resource Usage
This routine uses the I/O Timer and interrupts are disabled during the pulse generation. However, RTC
ticks will be accumulated during the pulse generation and the RTC will be updated when the process is
complete. If the pulse is too long characters being sent or received on serial channels 3-6 may be
garbled.
Example
Dim width as Integer
Call PutPin(12, zxOutputLow)
Call PulseOut(12, 2, 1) ' generate a positive pulse about 2µS long
Call PulseOut(0, 1e-5, 0) ' generate a delay of about 10µS
Compatibility
In the BasicX implementation, the RTC will lose time if the pulse is too long. Also, the BasicX
implementation does not support adjustable timing resolution.
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