Communication PCMK vs PLC 5/40

Dear experts,
Recently we installed a new control which is using Allen Bradley PLC5/40 (1785-L40B) (redundant processor & IOs).

During the project phase, the logic inside the PLC (downloaded by someone else) was accidentally wiped out.

I tried to use our pramming terminal but failed to communicate. RSLinx did not detect any PLC. We are using PCMK card. I've tried to access other existing PLCs with the same PCMK card and OK.

I noticed that there were two DIP switches at the back of the PLC. SW1 & SW2. Was it because of this DIP switch configurations? It (sw1) was set at MSD = 0, LSD = 0, Baud Rate 57.6Kbd. What configuration should I set for PCMK? Thanks.

Are you using the Traditional 9Pin to Mini-Din Plug? You need to use this on the PLC5 series using the DH+ channel A connection configured in RSlinx. Otherwise, you can use a 9-25 pin serial connection in RSlinx using DF1 connection on channel 0.

Let me know if you still need help,

Yup! I still need help.

I'm using the 8/9-mini DIN port (the one with round shape). I've tested on other PLC (PLC5/40C) and it worked, but not on this one. (PLC5/40)

Is your Channel A configured for something else?? Usually, the CH A is configured for DH+, but is completely configurable in the RSlogix code.
Look at the OFFLINE image that you have and click on Channel Configuration Properties. Make sure that the CHANNEL A is not INACTIVE, RIO or RIO Scanner enabled. If they are, you cannot communicate through channel A. You must communicate through the DH+ link on another unit connected in the network...if this is the case.
The most faithful connection is the Channel 0, which is often not used. This is the DB9-25 pin connection, that is sometimes covered on the front of the 5/40. (the DB25 on the processor)

I am at work until 330, so let me know...

Thank in advance.

Yes, both 1A & 1B (3-wire, are connected to somewhere) are used.

I've checked in the logic and the 1A was configured as DH+. Do I have to change it to RIO scanner? What effect will it have on the used 1A & 1B channels?

Channel 0 was not used. BUt I need to have different type of cable + some configuration to communicate. BUt I'm willing to learn it if there's no other options...

You should try to change the adresse of your programming terminal. RSLINX, configure driver.... If your terminal is set with the same adresse that the plc, you are not able to see the plc on the network.
I hope it will help you...
Vincent.
Belgium

Thanks...

After reading all the replies, I've checked with the Help file and compare with my other logic.
It seems (only my theory) that the Channel configuration was set at DH+ but the Diagnostic File was set to 0. The Help file says that 0 if we want to disable the channel. So eventhough it is set at DH+, if the Diagnostic File is zero, it is the same as we disable the channel.

It also says that the Diagnostic File must be the unused data file. I'm not sure whether it is refering to the N intiger, F or etc...

Oh.. one more think, changing the address at my programmingterminal will be last option as I'm afraid it will interrupt the communication with other PLCs.. We have about 12 AB PLCs.I'll be in deep trouble if that happen

Don't Disable the Channel!!! You will lose comms to the other devices......

Don't change the configuration of the Channel Either!!
As PacMan explained, check to see if the PC is set at the same address as the PLC/s.

RSlinx browser should see the other networked devices, regardless of the address collision. You say a redunant PLC....are you using the Redundant Communication card in both racks??...tied together DH+?


DB25male/wpins-DB9female/w/o pins is a straight cable, as far as I remember....
P/N AB VC P965 or MDC 1797.

You can make your own. Go to AB website and look for cables....

Hehe... Actually it was originally set to be zero, meaning that it was disabled. Nobody know whether it was working previously.

My plan is that I'll just put some value there, ie 72 (N72 data file, not use yet) and see what happen.

Thanks also for the alternative. I'll do that once the opportunity comes.

I'll let you know the results.

Thanks again.

Did I say that I want to change the Diagnostic File? Another "haha" to me. To do that, I need to communicate first!
How do I check my PC address. The PLS has MSD = 0 and LSD = 0. Baud Rate 57.6K. I got them from the dip switch on the PLC....

Look at RSWHO in Linx. Open the driver for your PCMK card; you should see something looking like a computer with a description like "Workstation, 00". This will be your PCMK card and it's node address. Make sure it's address is not set to an address used by the processor you're trying to connect to.

You have an unusual and complex system if you are using a redundant PLC-5/40B. You are also using the redundancy modules, called 1785-BCM's, and maybe even redundancy expanders, 1785-BEM's.

The way that these redundancy modules handle DH+ is that you set up both PLC's for the same node number. The 1785-BCM interprets all the DH+ packets coming through it and sends the ones for the pair's node number to the Primary PLC, and the ones for the pair's node number +1 to the Secondary PLC.

In your case, it sounds like both PLC's are set for Node 00. The Primary PLC will be Node 00, and the Secondary PLC will be Noode 01.... IF you are accessing the system from outside the 1785-BCM modules.

Because you are plugging into the local DH+ access port (the 8-pin Mini-DIN) on the PLC-5 itself, you are only going to see Node 00.

Because RSLinx defaults to Node 00, you probably have a simple node conflict.

The easiest way to resolve this is the disconnect this PLC-5 from the network (just unplug Channel 1A) and plug your 1784-PCMK cable into Channel 1A with RSLinx set for a different node number. I usually set it for 1, but you can any other node number up to 77.

It would also be a very good idea to get a pair of EEPROM plugs for these PLC-5's so this doesn't happen again.

Yes, there's only one icon "Workstation 00".
I think the PLC address is "00" based on the SW1 dip switch configuration. I'll try to change it another address. Appreciate if you could tell me how to change it.

I guess our system really is an unusual system, installed redundantly, PLC5/40 (1785-L40B/E Rev W01). They are installed on a separate rack, with redundant IO racks.Both have 1785-BCM installed on each PLC rack.

What I have tried yesterday, I pulled out the 1785-BCM module, I pulled out both 1A & 1B channel wires leaving only the processor and some more modules on the rack but still unable to detect.
I just didn't change the address.I'll do that this monday and see what happen.

TQ.