micrologix 1200 modbus programming problem of loss comunication

In micrologix1200 I have only one communication channel so that I do not unable to configure the PLC with Modbus rtu slave driver without losing communication with ml1200. Any tips on how to get around this problem?
I'm using rslogix 500 and in configure the Modbus rtu slave driver and download the program to the plc, the plc does not execute the program and not go the go online mode.

The MicroLogix 1200 has a "default COMMs" button that temporarily over-rides the program settings for the Channel 0 serial port.

When you press that button and the "DCOMM" LED turns on, the port will be set for the default DF1 Full Duplex settings and you will be able to go online with the controller.

Press the button again so that the DCOMM LED turns off, and the port will be set for the Modbus RTU configuration in your user program.

Ken Roach said:

The MicroLogix 1200 has a "default COMMs" button that temporarily over-rides the program settings for the Channel 0 serial port.

When you press that button and the "DCOMM" LED turns on, the port will be set for the default DF1 Full Duplex settings and you will be able to go online with the controller.

Press the button again so that the DCOMM LED turns off, and the port will be set for the Modbus RTU configuration in your user program.

Click to expand...

But even downloaded to the ml1200 a simple program (one input and one output) plc does not execute if the channel driver used is Modbus RTU slave so that the RUN LED does not turn on.
I use the Modbus rtu slave because I intend to develop a simple SCADA using the Modbus communication jamod api for java, then thought the PC would be the master and the plc would be the slave

When you download the program, RSLogix 500 should warn you that the serial communications configuration is different and that you will lose your connection.

The download still completes; the program is loaded into the controller.

To get online and switch the controller into RUN mode, you need to:

1. Press the DCOMM button until the DCOMM LED turns on.
2. Go online using DF1 Full Duplex protocol.
3. Switch the controller into RUN mode.
4. Go offline.
5. Press the DCOMM button until the DCOMM LED turns off.

If you need a controller that supports Modbus RTU at the same time as DF1, you need the 1200R two-port controller at a minimum. The MicroLogix 1100 and 1400 are also good alternatives because you have another Ethernet port.

With the single-port MicroLogix 1200 you can switch between Modbus and DF1 with the DCOMM button, but you cannot do so automatically or run both protocols simultaneously.

Ken Roach said:

When you download the program, RSLogix 500 should warn you that the serial communications configuration is different and that you will lose your connection.

The download still completes; the program is loaded into the controller.

To get online and switch the controller into RUN mode, you need to:

1. Press the DCOMM button until the DCOMM LED turns on.
2. Go online using DF1 Full Duplex protocol.
3. Switch the controller into RUN mode.
4. Go offline.
5. Press the DCOMM button until the DCOMM LED turns off.

If you need a controller that supports Modbus RTU at the same time as DF1, you need the 1200R two-port controller at a minimum. The MicroLogix 1100 and 1400 are also good alternatives because you have another Ethernet port.

With the single-port MicroLogix 1200 you can switch between Modbus and DF1 with the DCOMM button, but you cannot do so automatically or run both protocols simultaneously.

Click to expand...

RSLogix 500 warn me that the serial communications configuration is different and that i will lose my connection.
The download still completes; the program is loaded into the controller.
But the simple program doesn't turn on the LED RUN of ML1200.Why?
The program toggles the key(input I:0) and activates the output(O:0) does not work.

Ok I will do some tests.

This is just an inconvenience that comes with setting the Channel 0 port on a single port controller for Modbus instead of the controller's native protocol.

Perform the download and use the steps I described to get online, go into Run mode, and switch back to Modbus.

yuri90 said:

...RSLogix 500 warn me that the serial communications configuration is different and that i will lose my connection.
The download still completes; the program is loaded into the controller.
But the simple program doesn't turn on the LED RUN of ML1200.Why?...

Click to expand...

Just to be specific...

The controller will not automatically go to Run Mode after a download. Normally, when you are connected via the same driver as the program will use, you will download and then it will ask if you want to...

"Change Back to Run Mode?" ...

You select Yes and the it asks...

"Do you want to go Online?"...

etc.

Because of the difference in the driver that your computer is initially using to connect to the controller's port, and the driver the same port is configured to use after downloading, you are losing the connection before you get to the prompts above. So you cannot place the controller in Run Mode.

Follow Ken's very clear instructions to temporarily set the ports driver to default DF1, set the controller to Run Mode, and then set the ports driver back to user configured.

Regards,
George

Geospark said:

Just to be specific...

The controller will not automatically go to Run Mode after a download. Normally, when you are connected via the same driver as the program will use, you will download and then it will ask if you want to...

"Change Back to Run Mode?" ...

You select Yes and the it asks...

"Do you want to go Online?"...

etc.

Because of the difference in the driver that your computer is initially using to connect to the controller's port, and the driver the same port is configured to use after downloading, you are losing the connection before you get to the prompts above. So you cannot place the controller in Run Mode.

Follow Ken's very clear instructions to temporarily set the ports driver to default DF1, set the controller to Run Mode, and then set the ports driver back to user configured.

Regards,
George

Click to expand...

Ken Roach said:

This is just an inconvenience that comes with setting the Channel 0 port on a single port controller for Modbus instead of the controller's native protocol.

Perform the download and use the steps I described to get online, go into Run mode, and switch back to Modbus.

Click to expand...

Ok thanks, I'll do some tests if I have no problems related to it then'll be all right.(sorry for my english).

How to know if the PLC is responding Modbus requests?

Geospark said:

Just to be specific...

The controller will not automatically go to Run Mode after a download. Normally, when you are connected via the same driver as the program will use, you will download and then it will ask if you want to...

"Change Back to Run Mode?" ...

You select Yes and the it asks...

"Do you want to go Online?"...

etc.

Because of the difference in the driver that your computer is initially using to connect to the controller's port, and the driver the same port is configured to use after downloading, you are losing the connection before you get to the prompts above. So you cannot place the controller in Run Mode.

Follow Ken's very clear instructions to temporarily set the ports driver to default DF1, set the controller to Run Mode, and then set the ports driver back to user configured.

Regards,
George

Click to expand...

Thanks guys for the latest tips, I did what I was told and the plc really went to run mode and are running normally
but the COM1 port is still used by RSLinx so that my java application can not open the connection
When I try to open the connection I have the access denied error and really
RSLinx is using the port(process RSlinx.exe, RSlinx classic communicatons server).

When I finalize the process and try to send the request Modbus readcoils (B10: 0) I do not get answers.
Error msgs:
Last request: 01 01 00 01 00 01 ac 0a
Error reading response
execute try 1 error: I/O exception - failed to read
Last request: 01 01 00 01 00 01 ac 0a
Error reading response
execute try 2 error: I/O exception - failed to read
Last request: 01 01 00 01 00 01 ac 0a
Error reading response

obs:
When I follow the instructions of ken in step 2:
"* 2. Go online using DF1 Full Duplex protocol."
I simply click on "go online" with the LED DCOM on

Thanks in advance.