Modbus Timeout Error (SLC,RS485)

I've been stuck on an issue for a few hours now and the in-house expert is out at the hospital so I have to solve this on my own this time:

On the PLC, both err1 and err2 lights are on. I'm not using port 1, so err1 doesn't frighten me. On port2, I have a RS485 mini network set up which is nothing more than the connector, a 3-conductor interface, and the modbus device in question ( a Basler generator monitor).

- Yes, the jumpers on the 3150 are set to 485
- Yes, there is a terminating resister
- Yes, I tried port 1
- Yes, (i'm told) the setup in RSLogix is right, as it's been copied from previous projects which worked.

The MCM error file gives me an 8, which is a Timeout Error, and according to the manual, that already eliminates port and configuration issues (which are 16 and 18).

The crappy little 3-conductor cable I use passes my ohmmeter test, so it's a good cable.

Can anyone give me a push?

I have not heard of a SLC capable of RS485 and Modbus.

Did I miss something?

because you must have not seen the part of the post I forgot to type which is this:

....using a Prosoft 3150 mcm...

Ot...

Mark did the Keyspan adapter work??

check your PM's and send me your email

You know what's funn?

Recently, I connect my PC=>>232-485 converter=>>Automation Direct DL06.

I used only about 6 ft of comm cable between the two with 120ohm resistor on each end. That setup doesn't work until I removed one resistor. The setup also work when I remove both resistors.

It might have to do with 6ft of cable being to short to have an instrinsic impedance.

So if your cable is also short, try removing the resistors.

you had a terminating resistor on EACH end of that small network?

It was a good idea, i removed the resistor, still no joy.

If the error light is on you have a configuration issue.
The error light is off once the card is configured correctly wether the slave end of it is hooked up or not.
Remember the config only transfers over to the MCM from either warm start or when forced over internally.
If you want to send me the ladder file or post it on here we can have a look and see whats going on.

The error I'm getting in the MCM error is 8, which the manual says is Timeout. The configuration errors are 16 and 18.

Are you saying that maybe a configuration error is making it try to talk to the wrong device or something?

I simply don't have much experience in modbus, and the normal guy is out.

Have you sonnected to the cnfg port and gone in via Hyperterminal?

There is quite a thorough troubleshooting section in the user manual. Please post what colour each LED is (CFG, P1, P2, APP, BPACT, OK & BAT) and what number you are seeing in the ports config word. If you could also post the ladder file it would help immensely.

These Prosoft cards, especially the SLC ones are notoriously pedantic to get functioning, so be patient!

I agree with the previous post, the Prosoft gear is hard to get started. If this is a new install you should call their tech support line--very good people there and they can usually get you going.

If this is an older install, and you haven't done something like moved the card to another slot, I'd go in and look at all of the config registers to make sure you're sending the correct data to the card when it boots-up.

The cfig-err lights are telling you exactly that, you have a cfig-err. Once a good cfig has been loaded into the card the light will go off regardless of whether the port is in use.

Check whether comms settings match

Have you verified the comms setting?

1. Baud rate
2. Parity
3. Number of bits
4. Number of stop bits

well, i got it to work on Friday.

The error was 2-part: the modbus device i was talking to had an address changed since i last verified it (ugh!), and secondly, when i hook everything up on Modbus, one of the devices required a polarity switch to "partially" work. The Prosoft card now has a flashing err light, irregularly, so it's acting like a collision is still taking place. Removing the offending device also stops the error light flash, and the offending device has been verified and reverified.

But, even with it, i'm now getting data.