Micrologix 1100 - Handling (Non DF-1) Serial Comms

Hello all,

A quick question. Can this PLC handle a custom RS-232 (or perhaps even RS485) protocol? I need to chop the incoming Bytes and process them individually to decode their values (Header, Address, Data0, Data2, .....Data31, & checksum byte) message blocks are always 35 bytes long. I see no way to do this with the existing port on the MicroLogix as I need it for Programming or to connect it back to the HMI at run time. Is there an add-on comm card available for the ML1100 that can communicate over RS-232 and allows me to chop up the bytes as needed? I also need to be able communicate both ways. (Send/Receive) Closest thing I can find is an ASCII card. Would this allow me to do what I am wanting to do here?

Thx.

What sort of an ASCII card do you see for the MicroLogix platform ?

You could do fixed-length strings with the serial port if you weren't using it for HMI.

Otherwise I think the way to do this would be with an RTA Automation gateway device. It will handle the fixed-length ASCII decoding and read and write to integer data table arrays.

http://www.rtaautomation.com/product/460etca/

Give RTA a call and be sure they can handle the CRC and fixed-length requirements.

RS232 and 485 are electrical standard, not protocol. I think you meant ASCII. ProSoft and others makes Ethernet/IP to Serial ASCII cards and I'm quite sure you can use MSG to interface with them.

RTA makes one as well and I have heard good thing about their ease of setup but haven't used one myself.

They all offer trial period so you can get one and try to see if it works for you.

Thanks Ken/harryting.

Sorry Ken, The ASCII card was not for the Micrologix 1100 but for the 1500 which uses the same I/O as the Compactlogix platform. Before I spend a lot of time chasing ghosts, needed to find out if that ASCII card will let me do what I am wanting. I have used RTA's gatewayss in the past to read data from Scales an they worked flawlessly. I will ping them as well.

Again, thanks.

The gotcha for a serial protocol with a CRC on the end is that there's no conventional "delimiter" character like there is with ASCII, where a frame usually ends with Carriage Return and/or Line Feed.

I know that bit me when I tried to implement a special Modbus-like protocol with the 1734-232ASC module. It supported fixed length frames, or delimiters, but not timeouts.

In your case the fixed length ought to make it do-able. RTA will be able to give you a good idea on which device is compatible with the MicroLogix 1100 and can do what you need on the serial side.

Thanks for that helpful tip Ken. I was not aware of a Delimiter not being used with transmissions using CRC.