MicoLogix 1500 and 1761-NET-ENI

OK here is what i have:

ML1500(DF1,Full Duplex,19200) connected to
1761-NET-ENI which is connected(via ethernet) to
4 Port Ethernet hub (port 1)
Hub Port 2 = PanelView 550(ethernet)
Hub Port 3 = Labtop Running RSLogix 500.

The PV550 appear to work great when it's plugged into the Hub by itself. The RS500 appears to work fine when it's plugged into the hub by itself.

Problem:
When I plug both the PV550 and Laptop(RS500) into the hub, I start getting read/write timeout failures on the PV550. They seem to communicate briefly but after a few minutes the PV will start timing out.

Any Help?

Does the Hub have a collision Light on it? If so when you plug both the laptop in and the PV550 does the light become very active?

Also check and make sure each device has a unique IP Address.

reply

NO, the hub does not have a collison light.
Yes, each device has an unique IP.
Labtop has it's own IP
PV550 has it's own IP
ENI has it's own IP

Anymore help, beacause i'm stuck in confused land.
Thanks!

Well my suggestions were purely from a networking point of view. I don't have any experience with that hardware. It sounds like there is some conflict between the PV and the Laptop though, do they still need Node numbers when you use Ethernet, if they do you might want to check that out.

Bottleneck !

I'm almost certain that you're hitting an RS-232 bottleneck. It's like the 4th Avenue exit off I-5 when the Mariners are playing on a sunny Friday afternoon.

The following steps should help your performance improve:

1. Increase the Interscan Delay in the PanelView 550 Communications Configuration. By default it's trying to get data every 100 milliseconds; increse this to 250 ms at least.

Try that step first and see if comms are satisfactory. The next two steps might increase performance a little more, but change your system a little more.

2. Increase the RS-232 data rate on the MicroLogix 1500 to 38.4 kb. This works fine with a short serial cable, and the Net-ENI will autodetect it. You'll have to reconfigure the speed of the RSLinx DF1-1 driver if you connect directly, though. You may also have to change the Stop Bits selection on the Micro1500; see the Net-ENI user manual for a note about that.

3. Make sure the "Comms Servicing Selection" box in the Channel 0 configuration for the MicroLogix is UN-checked. This can speed up communications for the MicroLogix, at a small decrease in program scan time.

The 1761-NET-ENI is a nifty bridge from a serial port onto a LAN, but it's not magic; it's actually a little bit slower than being directly connected via DF1 because it has to packetize each DF1 message. If you have two devices attached, you can expect a communications performance decrease.

more followup

Thanks for the reply, Ken.

I was in the process of changing the Scan Time in the PanelView 550 to 500ms when I saw your reply. I was thinking that 19200 was the max baud rate that the ML1500 could talk. I was wrong again.

I set the PV550 to 500ms scan time and the ML1500 to 38400 baud rate.
Everything seems to be working ok (not having any read/write time out failures).

Thanks everyone!
I Love this site!

Baud?

When I used the 1500 and ENI last year, the baud max was 19.2. Is the higher speed a imporvement to the net-eni or 1500? Or is it just an undocumented feature... Also...

Never use a hub. Period. They are old garbage, and are totaly unsuitable for an industrial network. Spend the extra 1.50 and get a switch instead. I was called into a shop that had 4 net-enis on 1500s and a wonderware system. It had lots of com issues. Changed thier hub to a switch, and they all went away. Hubs are suitable when there are only 2 devices total on the network.