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Old March 6th, 2017, 07:07 PM   #1

arbj is offline
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Parallel ports in Allen Bradley PLC


I am interested to know if PLCs have a parallel port implemented in them. The PLC is an allen bradley and has 8 digital input lines, a strobe, ready and acknowledge lines. The levels are all +24 VDC

I am curious to know if there is a standard implementation for this type of port. I have been asked to develop an interface for this, it will be very helpful if there are documentations available for the parallel port, I heard it being referred to as LPT port (printer port).

I can implement a parallel port interface easily in my design if documentation were available, but my problem how do I test this apart from using on the target PLC.

More specifically I am interested in knowing how can 16 bit data be strobed in using just 8 bits.

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Old March 6th, 2017, 07:16 PM   #2
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Which AB PLC?
Just because you can doesn't mean that you should...
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Old March 6th, 2017, 08:19 PM   #3
Ken Roach
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"Local Printer" LPT ports are from the era when Centronics dominated the dot-matrix printer business for IBM Personal Computers.

To my knowledge, no Allen-Bradley programmable controller has ever had a parallel data port on it.

There is no standard implementation of an LPT or parallel data port using ordinary 24V I/O. There's no "LPT library" or similar function.

In general, you need enough data lines to support your data size. If you want to do 16 bit data with one strobe, you need 16 data lines plus a strobe.
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