can't communicate with a slc 5/04 processor

Mueller34

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Jan 2022
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I am trying to connect to a machine in my facility for troubleshooting, but I can't make it work. I am using a 1761-clb-pm02 from allen bradley and have tried using the 1747-uic I have, and the belkin adapter the company has. Neither one has worked. I tried configuring as a new rs-232 device as I have in the past with a similar setup from the same OEM. I have changed the error checking, protocol, baud rate, and device in many different combinations to no avail. I'm being stretched a little thin right now and my brain isn't fully operational. Any advice would be helpful.

Thanks.
 
it takes a null modum rs232 cable or regular rs232 cable and null modum adapter. I have always used that and setup RSlinx to autoconfig or autoset parameters.
 
The UIC is for a Data Highway 485 (DH485) connection and the 5/04 does not have this by default. However, it's serial port could have been reconfigured as a DH485 port. In which case you could use the UIC.

The 1761-clb-pm02 cable isn't going to work. You will need a standard null modem type serial cable.

If the 5/04 is not configured to use it's serial port as DH485 then it would be configured by default as an RS232 port. In which case the null modem cable would be used to directly connect the PC to the PLC serial port. And of course your computer might need a USB to RS232 adapter since modern computers don't generally have serial ports anymore.

Be aware that USB to serial adapters may give you a COM port with an unusual number. I have a device that typically makes my serial port COM5 instead of the usual COM1 that a physical serial port often uses. You can usually dig into the Windows Device Manager and discover or change those settings.

OG
 
From your mention of a pm02 cable it sounds like you are trying to plug into the 8-pin round Channel 1 connector -- that's only for DH+ connection. Unless you've got a 1784-U2DHP handy you want to be connecting instead to the Channel 0 DB9 connector.

How you connect to it will depend on what the program settings for it are. If it's not in use then it's likely still the default DF1 and a standard null modem cable will suffice; if it's set for DH485 you'll want the 1747-UIC, etc.

If you've got an offline copy of the program you can check ahead of time what you'll need.
 
not sure what null modem is referring to I do have a standard rs232 extension cable that was given to me with gender adapters, does that work?

I do have an offline copy of the program from the OEM and the coms driver says 1794_U2DHP-1.

I do now I had the com port correct as my laptop assign com5 or com8.

Thanks.
 
ok took me a little bit to think this through. I do not have a null modem adapter available to me. I will need to get my hands on a 1784-U2DHP and then I will be able to connect. As for now I can work with the offline program to give some things to check.

Thank you all for your help
 
not sure what null modem is referring to I do have a standard rs232 extension cable that was given to me with gender adapters, does that work?

I do have an offline copy of the program from the OEM and the coms driver says 1794_U2DHP-1.

I do now I had the com port correct as my laptop assign com5 or com8.

Thanks.
It is not the driver last used to connect that you want to know, but the communication port settings. Open 'Communication Settings' under the project tree and select channel 0.

Apparently whoever programmed it did have a DH+ adapter and used it, but if you don't have one you can't connect through Port 1.

You may still be able to connect through Port 0 depending on its settings.

A null modem cable/adapter has pins 2 and 3 crossed. A standard straight serial cable will not work because both your PC and the SLC will be trying to transmit on the same pin.
 
There are straight-thru type serial cables and null modem type cables. Null modem swaps the transmit and receive connections on one end. So the data you transmit to me lands on my receive pin. It is important for bi-directional (full duplex) communications.

Gender changers simply change the male-female connectors. There are null modem adapters that look like gender changers. You can add that to a standard cable.

In the Ethernet world this is called a crossover cable.

And yes, the null modem cable is MUCH less expensive than a U2DHP. The Rockwell null modem cable is either 1746-CP3 or 1756-CP3. Hopefully you've got one of those laying about.

OG
 
Ok I found the configuration it says DF1 full duplex, source id 9, baud 19200, parity none, stop bits 1 l, and so on.

The oem will gladly supply me the $1500 cable...
 
Ok I found the configuration it says DF1 full duplex, source id 9, baud 19200, parity none, stop bits 1 l, and so on.
Then all you should need is a null modem cable (or adapter for your straight cable) with the RSLinx DF1 driver.

Of course, if something else (HMI for example) normally uses that port then you'll have to disconnect that whenever connecting with your PC. If that's a serious issue then you might consider the U2DHP, but if there's nothing currently using port 0 then I certainly wouldn't spend the money.
 
Then all you should need is a null modem cable (or adapter for your straight cable) with the RSLinx DF1 driver.

Of course, if something else (HMI for example) normally uses that port then you'll have to disconnect that whenever connecting with your PC. If that's a serious issue then you might consider the U2DHP, but if there's nothing currently using port 0 then I certainly wouldn't spend the money.

Cheap null modem cable is $7 US on Amazon. And others for even less :)


OG
 
thank you, I will get myself the null modem adapter so i can go online with this machine in the future.

side note, the machine should be good now that I found the cable the set up guy ripped out and jerry rigged back in place.

🍻
 
I had a long post all typed up talking about null modem cables and such but got called away before it was done and others answered far more succinctly.


https://en.wikipedia.org/wiki/Null_modem


I'm glad you were able to figure out the issue.


There are other ways to connect to the 5/04 if the serial port is generally occupied, but they all require more hardware that's generally expensive. If you're going to be doing online support of a bunch of 5/04s with serial HMIs, it would make sense to connect via DH+ using either the round mini-DIN or the 3-pole Phoenix connector. The first one I saw used a PCMCIA card, but those (and laptops that can use them) are long gone. Another method I saw, that was very effective and reliable, involved the use of a spare ControlLogix chassis with a -DHRIO and an -ENBT module in it. RSLinx would pass through the backplane to get to the machine. This is doable if you happen to have the hardware laying around but would be really expensive to set up from scratch (like about $9k list price). You can go with the -U2DHP module from AB, but...they're expensive and delicate. We had a couple fail just from normal use. We also tried the Prosoft AN-X2-AB-DHRIO gateway module with great success. They're also expensive, but they're very reliable and robust. Way more than AB's -U2DHP.


A more recent product is from Automation Networks:
https://*************************/o...lc5s-and-slc-504s-to-latest-ethernet-productsI've never used that one but it's definitely worth a try and priced at about half what we paid for the Prosoft version 3 years ago.



If you're only doing occasional work with a 5/04 and don't need to be online at the same time as a serial HMI, I would just stick with the serial cable. It's cheap, simple, and reliable. If you have a lot of 5/04s and want the HMIs to stay connected while you're online...you'll need a DH+ gateway. I would choose the AB -U2DHP last of all the options based on my previous experience with them being expensive, delicate, and not repairable.
 

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