# Rockwell Plc-5 polling Ascii devices over Ethernet

**URL:** <https://forums.digi.com/t/rockwell-plc-5-polling-ascii-devices-over-ethernet/7494>\
**Category:** Digi One IA/IAP\
**Created:** [June 1, 2007, 2:21pm UTC](https://forums.digi.com/t/rockwell-plc-5-polling-ascii-devices-over-ethernet/7494 "2007-06-01T14:21:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![CrazyIvan](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@CrazyIvan](https://forums.digi.com/u/CrazyIvan)\
**Post date:** [June 1, 2007, 2:21pm UTC](https://forums.digi.com/t/rockwell-plc-5-polling-ascii-devices-over-ethernet/7494/1 "2007-06-01T14:21:58Z")

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using [http://ftp1.digi.com/support/documentation/90000642\_a.pdf](http://ftp1.digi.com/support/documentation/90000642_a.pdf) as reference, I’d like to accomplish the same thing using a Plc-5.

My application would be using a Plc-5 to poll 2 weigh scales via a Digi IAP serial port 1 and 2.

Im having problems getting the poll message (write) to occur with no errors. I’m getting "connection broken’ messages at the plc-5 using the same address locations refrenced in the above document.

What type of Plc-5 message instruction would I use to accomplish this ? How would I accomplish selecting which serial port ( of the digi ) to route the poll response read data ?

Current Plc-5 model and firmware revision - Plc-5/40E Series E Revision G

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**Author:** ![lynnl](https://avatars.discourse-cdn.com/v4/letter/l/22d042/32.png) [@lynnl](https://forums.digi.com/u/lynnl)\
**Post date:** [June 1, 2007, 2:41pm UTC](https://forums.digi.com/t/rockwell-plc-5-polling-ascii-devices-over-ethernet/7494/2 "2007-06-01T14:41:35Z")

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We don’t have a PLC5 & even buying one used on ebay with RSLogix5 license was looking like a $10K investment, so the IAP firmware just assumes (hopes) that the PLC5 creates what the ControlLogix, SLC5/05 and MicroLogix 1200/1500 PLC create when they claim to be using PLC5 commands. This is noted in the Release Notes (which of course no one reads 🙂

Make sure you’re trying the latest firmware “F” - “E” for sure rarely works with PLC5 due to a too generic an idea of the System Addressing for PLC5

DOIAP is handling the subfunctions 0x67/68 (the Typed Rd/Wr) and 0x00/01 (Word Range Rd/Wr), but then the PLC3 and PLC5 add different forms of layered addressing within this command - this is where the problems seem to come in. If you just use the DF1 specs details, you end up with something PLC5 won’t permit. Only a subset of what the spec implies is permitted is allowed in real life. After this fun, I see why the SLC5/MicroLogix team created the much more predictable typed rd/wr with 3 address fields. Too bad the PLC5 team is “above” supporting a lowly SLC500 command.

Anyway, worst case you can attach a Wireshark/Ethereal trace of your PLC5 request and I can look at the byte form being used.

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**Author:** ![CrazyIvan](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@CrazyIvan](https://forums.digi.com/u/CrazyIvan)\
**Post date:** [June 1, 2007, 8:29pm UTC](https://forums.digi.com/t/rockwell-plc-5-polling-ascii-devices-over-ethernet/7494/3 "2007-06-01T20:29:19Z")

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thank you much for the quick response. We’ll discuss our options before deciding what avenue to pursue.

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**Author:** ![aerioch](https://avatars.discourse-cdn.com/v4/letter/a/5fc32e/32.png) [@aerioch](https://forums.digi.com/u/aerioch)\
**Post date:** [March 16, 2008, 12:15am UTC](https://forums.digi.com/t/rockwell-plc-5-polling-ascii-devices-over-ethernet/7494/4 "2008-03-16T00:15:04Z")

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I was having the same problem. I changed my communication command to “PLC-5 Typed Read to SLC”, and now it works fine. I am using a Series E / Rev. B processor.