ML 1000 to PC help

Hi Gang

I'm having trouble connecting a PC to connect to 2 Micrologix 1000's.

Here's the setup. I work at a small water plant. The main plant has an SLC 5/03 and a Micrologix 1500 connected via DH-485. These two units handle the distribution pumps, well pump calling, chlorination and the nanofiltration trains. There are two wells that each have a ML 1000. The plant 'talks' to the wells via Data-Linc LLM1100 modems on dedicated leased lines.

The modems interface with the PLC's via serial cables.

I've lost comms with the wells and I need to make sure that the PLC logic is intact before I send the modems off for repair. The lines check out OK per the phone company.

I cannot get the laptop PC (RSLinx Classic Lite 2.57.00.14) to link up with the ML1000 through a USB-1761-CBL-PM02. I just can't find the right combination of settings to make it go.

Is there something special that needs to happen because the ML uses the serial port to talk to the modem?

Is is possible to access the logic through the DH-485 PC?

Thanks for the help.

--Chris

Look at the communication setup in the offline project. That should give a clue.

bernie_carlton said:

Look at the communication setup in the offline project. That should give a clue.

Click to expand...

I've never seen the code for the well units. Another reason why I want to take a peek!

Bodo said:

I've never seen the code for the well units. Another reason why I want to take a peek!

Click to expand...

What are the modems connected to in the "plant"? Can you take a look and see what driver (protocol) is used to talk to the ML1000's. DF1, DF1 slave or?

Bodo said:

I've lost comms with the wells and I need to make sure that the PLC logic is intact before I send the modems off for repair. The lines check out OK per the phone company.

--Chris

Click to expand...

Are the Micrologix's happy/healthy and in run mode?

Mickey said:

What are the modems connected to in the "plant"? Can you take a look and see what driver (protocol) is used to talk to the ML1000's. DF1, DF1 slave or?

Click to expand...

The modem in the plant is connected to the RS-232 port on the SLC 5/03 via a 9-pin serial cable.

As far as the protocol goes, I don't know. TBH, my knowledge is limited. How can I tell?

Caveman said:

Are the Micrologix's happy/healthy and in run mode?

Click to expand...

Yes, It looks that way.

Bodo said:

The modem in the plant is connected to the RS-232 port on the SLC 5/03 via a 9-pin serial cable.

As far as the protocol goes, I don't know. TBH, my knowledge is limited. How can I tell?

Click to expand...

Look at the SLC 5/03's program ( channel configuration).

Post its .RSS file if you can and someone here can help (zip the file first).

You probably have a very tricky communication setup; MicroLogix 1000 with Half-Duplex Slave and maybe with hardware handshaking.

What is connecting from the plant control system to those remote MicroLogix 1000 controllers ? Is it a PC with RSLinx or another serial driver, or is there some sort of connection from the plant modem to the SLC-5/03 controller ?

See if your particular installation of RSLinx 2.57 includes support for the DF1 Half Duplex Polling Master driver. That's what you will need to talk to these MicroLogix 1000 controllers if they are set up for DF1 Half Duplex.

If this were my system I would actually be trying to connect the MicroLogix serial port to the serial port of an SLC-5/05 or ControlLogix so that I could try various serial port settings on Half Duplex Master. In ControlLogix it's very easy to "drill down" from Ethernet to the serial port, but trickier with SLC-5/05 or even SLC-5/03 controllers.

As I recall, the LLM-1100 modems supported 1200 baud half-duplex with RTS/CTS handshaking.

There were two complicating factors on the MicroLogix 1000 side.

The first was that early MicroLogix 1000 DF1-Half-Duplex firmware would not support the auto-detection feature where it would switch from DF1 to DH485 depending on what it saw on the serial port.

This was because the 1200 baud data rate for DF1 was too dissimilar to the 19200 data rate for DH485; it would work if you had DF1 Full Duplex at 9600 and DH485 at 19200, for example.

The other issue was that the Half-Duplex timing parameters and handshaking settings could only be configured online; they don't show up in the offline RSLogix 500 file.

So the configuration method was to write the program, download it over DF1 Full Duplex, then reconfigure the port for DF1 Half Duplex Slave with the appropriate handshaking and timing parameters. Then you had to switch to using the DF1 Half Duplex Polling Master driver.

This was all very fun stuff in 1997. In fact, I think that this is the exact issue that introduced me to fellow PLCTalk member Randy Maes, who taught me everything I know about serial comms.

I still have that box of LLM-1100 modem demos stashed in an attic box that I've promised to clean out.

Edit: Took a while to write this and get coffee. Examining the SLC-5/03 serial port configuration is a very good start.

Ah! Thanks

Here we go:

DF1 Half Duplex Master

Edit:

Here's the rss file https://drive.google.com/file/d/0B6VK5Ivq94dIWVNrQWl2ZTRaQW8/view?usp=sharing

Bodo said:

Ah! Thanks

Here we go:

DF1 Half Duplex Master

Edit:

Here's the rss file https://drive.google.com/file/d/0B6VK5Ivq94dIWVNrQWl2ZTRaQW8/view?usp=sharing

Click to expand...

Then more then likely the ML1000's are configured for DF1 Half Duplex Slave.
You will have to use the DF1 Half Duplex Master driver in RSLinx to get connected to the ML1000's with your PC.
Match the baud rate and make sure the PC has a different node address.

I think I mis-spoke. The laptop that I can take out to the wells has RSLinx Classic Lite on it. I don't see an option for master/slave.

Is it possible with that software?

LLM1100’s do max out at 1200 baud but have a feature called “Auto Sense Carrier Control” where when data is detected coming into the port, the processor buffers the data, turns the carrier on and then sends the data. This is the default setting so more than likely it is how they are still configured. With this, it’s a pretty safe assumption that the ML1000 will be a DF1 Half Duplex Slave without handshaking. With that said I’m not sure you can set the ML1000 to operate without handshaking but that shouldn’t matter. If the SLC5/03 is the master then all you need to do is look at either the polling table to determine the node addresses of the two ML’s or the message instructions (again for the node addresses). Once you have them then all you need to do is setup RSLinx as a DF1 Half Duplex Master and set the polling range to match the ML’s. If you’re going to talk to one at a time then simply set the polling range for a single node address and try each ML until you get the connection. You might have to jumper RTS to CTS on the PC’s side of the cable if you can’t set RSLinx for no handshaking.

As to the phone lines, 9 times out of 10 (99 out of 100 really) the phone company will tell you the lines are OK when they are not. They typically don’t send anybody out into the field to test, they just use diagnostic software that is not very good at finding problems. Ask them what the dB loss is between the two points. Another question to ask them is if the lines were converted from analog to digital. This is happening all over the country and before too long there won’t be any more analog phone lines. If this is the case there won’t be anything you can do with the LLM1100’s. They don’t work with digital lines even though there is an analog interface at each end point. The translation from analog to digital (and back again) squares off the FSK signal which corrupts it enough that the modems won’t recognize it as a valid signal. The number one tech support phone call for LLM1100’s is Telco related and it’s rapidly becoming an analog to digital conversion issue.

Give Data-Linc tech support a call. They can walk you through trying to figure out the PLC’s configuration as well as some tests you can run on the LLM’s.

Availability of the DF1 Half Duplex "Polling Master" driver has been spotty for years. First it didn't work, then it was in 32-bit only, then it was removed... it's not a popular driver and it relies on hardware access that Windows doesn't like to give. I have version 3.60 installed on Windows 7 32-bit and that driver is available.

I wouldn't install above version 2.59 on your machine; you don't want to go to 3.x without carefully reviewing your other software first because of a big change in how EDS files were handled.

Randy is right, of course, about the hardware handshaking. I see in the SLC-5/03 Channel 0 System Mode configuration that the SLC is set up for No Handshaking, and is using a "pre-transmit delay" of 30 milliseconds.

So that's good. If you can get a PC with the right driver, you should be able to connect.

The ladder code you posted reads and writes from DF1 Slave nodes 2, 3, and 4.

Only Nodes 2 and 3 are actually in the Poll List, so Node 4 depends on the MSG instructions getting through from the master in between polls. You'll also see that the logic only checks the Node Table for Nodes 2 and 3 before sending them messages. This suggests that the device at Node 4 might be disabled or absent, plus the fact that the OP says there are only two remote devices.