Micrologix 1400 RS 485/232 communication

Hello everyone, I have a micrologix 1400 series PLC ( 1766 L32BWAA) and it has 3 ports, port 0 (for RS232/485), port 1 ( LAN ,RJ45) and port 2 (non-isolated RS232) , now i have connected the PLC with my laptop using port 1 by LAN cable and I'm using it for programming the PLC. I also have a control card with RS 485 port( 2 wires) for communication, now i want to use those 2 wires of control card and somehow communicate with PLC, like sending commands from PLC to switch ON the pump, etc. How am i supposed to wire the connection and how do i communicate/program the same. I have a ADAM 4520 and ADAM 4521 converters, I'm thinking of using the same, will it work? I have RS logix 500 for programming, how do i use it to communicate with control card.

What's the reference of your control card with RS485?
Does it support Modbus RTU?
if so you can follow the steps in thes links
http://www.plcengineers.com/micrologix_modbus_rtu.html

http://static1.squarespace.com/static/5252ed6de4b0b9b7feb218da/t/525db663e4b097a84ebe76a7/1381873251006/PLC+Modbus+Config.pdf

Can you clarify what it is you are trying to do maybe even diagram it?

The ADAM 4520 is an RS-232 to RS-485 isolated signal converter.

The ADAM 4521 goes the other way; it's an 'addressable' RS-485 to RS-232 converter.

So those might be usable to connect a MicroLogix to some kind of non-addressable RS-232 device.

Please explain exactly what kind of "Control Card" you have and what you want to do with it.

tarik1978 said:

What's the reference of your control card with RS485?
Does it support Modbus RTU?
if so you can follow the steps in thes links
http://www.plcengineers.com/micrologix_modbus_rtu.html

http://static1.squarespace.com/static/5252ed6de4b0b9b7feb218da/t/525db663e4b097a84ebe76a7/1381873251006/PLC+Modbus+Config.pdf

Click to expand...

Yes it does have modbus RTU support, the links that you've sent resemble what I wanted to achieve, I'll give it a try and see what happens. Thanks.

I followed the procedure given by tarik1978 but i have another issue now. The control card sends information on modbus addresses and i have the list of addresses along with expected message at that address. Now my task is to map those modbus addresses to the PLC tags such that when a command is received say on modbus address 40001 then i some tag linked to that address gets changed from NO to NC ( binary values are expected at address 40001) .How do i map or link the modbus addresses with PLC, do i need something else, am i missing something?

I'm using the channel 0( mini 8 pin ) of PLC and 1763 NC01 for communication , 2 wires are used from the RS485 pins of the control card and connected to 1763 A and B pins which is then connected to PLC.

What else do i need? I just want to communicate between the card and PLC.

Example- The control card is connected to a test setup with switches for simulating faults. If i simulate a fault using the switch and connect GUI to the RS 485 port of card then the RS 485 sends the information on GUI and i can see that thw fault has occurred. Now this thing should happen in PLC,the PLC tag must indicate the arrival of fault.

Did you configure channel 0 to be a Modbus RTU Master?
Did you configure a local message in your Micrologix 1400? if not follow the steps in this document starting from page 400:https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1766-rm001_-en-p.pdf

Also set Channel 0 handshaking mode for "No Handshaking (485 Network)"
if theere is no communication try swapping line DATA A & DATA B

You can find in the bellow link a a sample program for Modbus using Micrologix 1400
https://rockwellautomation.custhelp.com/app/answers/detail/a_id/34077

tarik1978 said:

Did you configure channel 0 to be a Modbus RTU Master?
Did you configure a local message in your Micrologix 1400? if not follow the steps in this document starting from page 400:https://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1766-rm001_-en-p.pdf

Also set Channel 0 handshaking mode for "No Handshaking (485 Network)"
if there is no communication try swapping line DATA A & DATA B

Click to expand...

I followed the instructions given,but there seems to be an issue. This thing is totally new to me. I had configured channel 0 as Modbus RTU slave initially but now i am using it as Modbus master, the handshaking mode was already set to "No handshaking(485 Network)" . I need some more help with the local messsage configuration in program.

I know that when i toggle a switch the same is reflected at modbus addres 40009 and i have configured the msg block accordingly. But i still cant read anything, however when i send something and check the channel status, i can see messages being sent. Also i am confused about the holding registors, where exactly can i see that something has arrived on modbus address 40009? Isn't there a simple way? like i recieve a word in 'N' register and then see what have i recieved or from where have i recieved.

If you have some more literature on this please share it.

i have attached what i have so far.

There is a timeout error, that means the Master device does not get a reply from the Slave device, check this thread for similar issue:http://www.plctalk.net/qanda/showthread.php?t=72944

Check this KB:MicroLogix 1100 Communications via ModBus
https://rockwellautomation.custhelp.com/app/answers/detail/a_id/33774

It is still not clear to me whether your "control card" is a Modbus RTU protocol "Master" or "Slave" device.

You cannot configure or troubleshoot your MicroLogix connection until you have clearly defined that role.

I believe that your "control card" is a Modbus RTU Master, which means you will configure the MicroLogix as a Modbus RTU Slave.

If you can provide more details about the "control card", you can get better advice on how to configure the MicroLogix to work with it.

There is an entire Modbus.org website dedicated to the protocol itself. You absolutely must know whether your device is a Master or a Slave before you can begin working with Modbus.

RJ29 said:

Also i am confused about the holding registors, where exactly can i see that something has arrived on modbus address 40009? Isn't there a simple way? like i recieve a word in 'N' register and then see what have i recieved or from where have i recieved.

Click to expand...

Have you mapped the Modbus registers to Integers?