Modicon Master to A-B MicroLogix 1100 slave

We built a pump control panel for a municipality that is now using Modicon TCP protocol for thier SCADA communications.
I understand from AB that Comm Port 0 (DF-1, RS-232) can be configured for Modbus. However, they prefer to use Ethernet in lieu of the hard wire terminal cable AB recommends.
Can anyone help me with this? I'm at a loss as how to configure (map) the AB I/O and some data storage registers (N7:xx)so the Modbus master can read and write to and from these registers.
Any help would be greatly appreciated.
Thank You

Are you asking for Modbus TCP or Ethernet/IP? If so, the ML1400 now supports Modbus TCP, but you will need a SERIES B controller to utilise the protocol.

Both the ML1100 & ML1400 support Modbus Master/Slave via RS232 or RS485 (CH0) so you should be pretty well covered.

Hope this helps.

Rob

Right, the MicroLogix 1400 Series B hardware (and firmware) supports Modbus/TCP natively on the Ethernet port, but the MicroLogix 1100 does not.

Since it took a Series change (probably a new Ethernet daughtercard) to get this functionality in the MicroLogix 1400, it is very unlikely that RA will add Modbus/TCP to the existing MicroLogix 1100 hardware.

You're going to need to use a Modbus/TCP to serial converter, or a Modbus/TCP to EtherNet/IP converter. The serial converter is cheaper and simpler.

There are a handful of Ethernet/Serial bridges that implement Modbus/TCP to Modbus/RTU: Google will show you a dozen of them.

To cut through the clutter, I can recommend three of these devices:

Lantronix XPress-DR-IAP

Digi One IAP
RTA 460MSMM

The Lantronix XPress-DR-IAP is least expensive but more complex to configure.
The Digi One IAP is more expensive, more flexible, and medium-complexity.
The RTA 460 MSMM is slightly more expensive than the Digi One but is extremely easy to configure.

In any case the price window is only between about $350 and about $550, so in my opinion ease-of-use should be weighted heavily in the decision to buy Qty.1.

This is all presuming that you have the Channel 0 serial port of the MicroLogix 1100 available to connect to the Ethernet/Serial interface. If not, you have to go with the Modbus/TCP <-> EtherNet/IP interface, which is a different set of products. The Digi One IAP happens to fall into both categories.

When you configure Channel 0 as a Modbus RTU Slave port, RSLogix 500 lets you select an Integer data file for each Modbus data type. Typically I just select the Modbus Holding Registers (4xxxx) to be "N40:xx" and use those in my program. There isn't much else to it.

Another option is the Schneider Ethernet/IP devices. You didn't list hardware (Quantum, Premium, M340) but they all have Ethernet/IP capable ethernet devices. Since the ML1100 uses a vendor extension to Ethernet/IP (PCCC encapsulated), I would suggest you explicit message from the 1100 to the Schneider device, and you could use the CIP Modbus object to read/write all the standard Modbus registers.

It is possible to message the other way, but it is a lot tougher. The ML1100 does not support implicit messaging either as scanner or slave, that (easy) method is not available. I do not think any of these Schneider solutions will come close to the price points that have been described already, so that may be a major consideration.

NOTE: assumed Modicon meant Modicon PLC... a re-read says might just be ModbusTCP, so this doesn't apply.

AB dragged thier feet for a long time before offering even the most basic Modbus connectivity built-in (no need for an encompass conspirator component). They sure as hell didn't make it very clear how to use the Modbus functionality they added. Notice they did not add Modbus TCP (almost the same damned thing) to the Ethernet interface. Again, product engineered with profit in mind...not functionality. Anyhow, I've used the 1400 on the RS485 lines talking to 2 AB AC drives. AB has a tech note on this and if you follow it to the T; it won't work. The ML nails the line so fast and often that there are collisions. You must put in some delay between messaging(0.1 sec is fine). Works fine with that.