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-PWM
The
DY,PM
and
FQ
commands
1
are used on the RIO-47xxx to output 3.3 V PWM signals on
Digital Outputs 14 and 15. These outputs are normally optoisolated, which limits the PWM
frequency to a maximum of 50 Hz. The -PWM option bypasses optoisolation and provides
buffered outputs for Digital Outputs 14 and 15, increasing the maximum frequency to 20 kHz.
The location of the reference ground for these signals will vary from model to model, see Table
A.8 for the reference ground connections on models that include the -PWM option.
1
These commands are only available on firmware Rev 1.1d and above.
RIO Part Number
Connector
Label
RIO-47122
Pin 41 on 44 Pin D-Sub Connector
N/C
RIO-47142
Pin 41 on 44 Pin D-Sub Connector
N/C
RIO-47202
Screw Terminal
AGND
RIO-47300
Screw Terminal
GND
Table A.8: Reference Ground connections for PWM signals
The PWM output frequency is set with the
FQ
command. The actual output frequency
f
a
measured at Digital Outputs 14 and 15 can be calculated as shown below.
•
10 – 311 Hz
In this frequency range,
f
a
is equal to
FQ
, accurate to ±1 Hz.
•
312 – 20,000 Hz
In this frequency range,
f
a
is calculated as shown below in Figure A.3, accurate to
±0.1 Hz.
The rounding function results in a frequency resolution that is dependent on the commanded
frequency FQ. This relationship is shown in Figure A.4.
Appendix ▫ 88 RIO-47xxx Rev. 1.0r
Figure A.3: Output frequency calculation for
frequencies 311 - 20,000 Hz
f
a
=
80,000
Hz
@ RND
[
80,000
Hz
FQ
]
Figure A.4: Commanded Frequency FQ vs F
a