Micrologix1200 comunication problem

Hi, all.
We have a MicroLogix1200, which channel configuration is "Driver: DH485; Node Address: 1; Baud: 19200; Network Link ID: 1". This channel is used for a HMI.
Today, I tried to connect to the PLC with my PC. Firstly, I push the comm switch to "DCOMM". Then, I tried to auto config the RS232 DF1 driver in RSLINX, and it was successful. But RSLINX just could not find the PLC at all.
Then I tried to restart the RSLINX, the PC, the PLC, and it still could not work.
Finally, I tried other drivers, and the DH485 UIC driver worked. The RSLINX found about more than 20 MicroLogix1200s, and they were same, and they were just the PLC I wanted to connect to.
Is there anyone can tell me what happened, and why? What is the DH485 UIC driver, and why it can work when I switch to "DCOMM" ?
Thanks in advance.

Exactly what physical interface are you using ? Is it a 1747-UIC or some other sort of serial port ?

If you want to connect to the MicroLogix 1200 using DH485 protocol (the way it is configured and communicating with the HMI) you should use a 1747-UIC and the 1747-UIC driver.

If you are using a standard serial port or a general-purpose USB/RS232 converter, you should press the DCOMM button until the DCOMM LED turns on, then use the DF1 RS232 Devices driver, set for DF1 Full Duplex, 19200 baud, No Parity, 1 Stop Bit, CRC Error Checking, SLC/MicroLogix device type.

Ken Roach said:

Exactly what physical interface are you using ? Is it a 1747-UIC or some other sort of serial port ?

If you want to connect to the MicroLogix 1200 using DH485 protocol (the way it is configured and communicating with the HMI) you should use a 1747-UIC and the 1747-UIC driver.

If you are using a standard serial port or a general-purpose USB/RS232 converter, you should press the DCOMM button until the DCOMM LED turns on, then use the DF1 RS232 Devices driver, set for DF1 Full Duplex, 19200 baud, No Parity, 1 Stop Bit, CRC Error Checking, SLC/MicroLogix device type.

Click to expand...

Thank you, Ken.
I just used a common rs232 cable to connect the PC and the PLC.
And I am sure the DCOMM LED was on, and the auto configuration had been successful, and it just cannot work.

The MicroLogix 1200 controller requires a 1761-CBL-PM02 cable. This is the ordinary programming cable that fits all MicroLogix controllers.

The best way to connect to a MicroLogix 1200 controller is:

1. Connect your PC serial port to the controller's Channel 0 port with a 1761-CBL-PM02 cable.

2. Press the DCOMM button until the DCOMM LED comes on. DCOMM only affects Channel 0.

3. In RSLinx Classic, select the proper COM port and configure a DF1 RS-232 Devices driver.

4. Configure the driver for 19200 baud, no parity, 1 stop bit, CRC error checking, and SLC/MicroLogix Device Type. The Autoconfigure feature may work as well.


If you have done all of these things correctly, and the controller is not damaged, then RSLinx Classic should be able to communicate with it.

Ken Roach said:

The MicroLogix 1200 controller requires a 1761-CBL-PM02 cable. This is the ordinary programming cable that fits all MicroLogix controllers.

The best way to connect to a MicroLogix 1200 controller is:

1. Connect your PC serial port to the controller's Channel 0 port with a 1761-CBL-PM02 cable.

2. Press the DCOMM button until the DCOMM LED comes on. DCOMM only affects Channel 0.

3. In RSLinx Classic, select the proper COM port and configure a DF1 RS-232 Devices driver.

4. Configure the driver for 19200 baud, no parity, 1 stop bit, CRC error checking, and SLC/MicroLogix Device Type. The Autoconfigure feature may work as well.


If you have done all of these things correctly, and the controller is not damaged, then RSLinx Classic should be able to communicate with it.

Click to expand...

Ken, yes I have done all the steps, and it did not work.
And when I tried DH485 UIC, it worked.
That is the question.

The 1747-UIC driver is essentially a pre-defined DF1 Full Duplex driver that sets the Device Type for "1770-KF3/1747-KE", so that it browses node numbers 0 through 31 over DF1. The 1747-UIC then converts DF1 to DH485, so the driver browses node numbers 0 through 31 on DH485.

That's why you saw "20 MicroLogix controllers" when you browsed using the 1747-UIC driver (but not actually a 1747-UIC), because the MicroLogix is set for DF1 Full Duplex so it will respond to a message addressed to any node number.

The DCOMM feature always sets Channel 0 for 19200 baud, no parity, 1 stop bit, CRC, Full Duplex, SLC/MicroLogix device type. If you set up your DF1 Full Duplex driver for those settings, it should communicate.

All I can suggest is to double-check the DF1 driver settings. Maybe if you can post a screenshot of the DF1 driver configuration, somebody here on the Forum can see which setting is incorrect.

Thanks Ken.
I just used the auto config function of the RSLINX, and it said successful.
So I don't know why my DF1 setting could be wrong.

What are the settings that DF1 Autoconfiguration returned ?

I've never seen it detect port settings wrong, but I suppose it's possible.

I recently had a problem with the autoconfigution. Using a USB to serial converter (from Rockwell). It was configured the first time with one USB port. But I tried to use another one to connect the laptop to a PV1400. The autoconfiguration succeed and RSLinx found the PV1400 but when I tried to ulpoad the application, it stayed in the element recognition. I changed the cable of USB port and after applying change in RSLinx, it just worked fine.

I am very sorry. These days I was very busy, and until today I have time to reply.
I have checked my DF1 config, it was "19200,no parity,1 stop bit, CRC, Full Duplex, SLC/Micrologix device type". So the DF1 configuration was OK. But the DF1-RS232 driver did not work.
And another question, while I selected Press DCOMM button, why I can connect the PLC with DH485 UIC driver? That is contradictory.

When you pressed the DCOMM button (and the DCOMM light turned on) you were setting the Channel 0 serial port of the controller to the default settings of 19200 baud, no parity, 1 stop bit, CRC error checking, Full Duplex, DF1 address 1.

These settings are compatible with the 1747-UIC driver, even though you do not have a 1747-UIC device. As I explained before, the 1747-UIC driver is essentially a pre-configured DF1 Full Duplex driver that has the Device Type set for '1747-KE/KF3", which browses multiple remote nodes. That is why you saw many icons for the MicroLogix controller.

When you say that the 1747-UIC driver 'works', do you mean that you are able to go online with the controller, or do you just mean you are able to browse the controller and see multiple entries in the browse ?

I cannot explain why the correct settings in the DF1 Full Duplex driver do not appear to work for you, or why the Autoconfigure feature does not work. You may have a defective or damaged or incompatible serial port or serial device. You have performed all of the configuration steps that I can think of correctly.

Are you using a USB/RS232 converter ? Many of the inexpensive ones do not work well with industrial software, particularly RSLinx and the Autoconfigure feature.

Ken, I can use DH485 UIC driver to go online with the controller.
I am sure the serial port is OK, because I can use it to connect other PLCs well.
And my PC, Dell E5500, do have a RS232 port.
I guess maybe there is something wrong with the PLC's DCOMM button. When I pressed the button, the light turned on but the channel did not change to default settings.

Do you have one of the MicroLogix 1200 controllers with a second 'HMI' serial port on the right side ?

Channel 0 is the conventional serial port that faces up, on the left side of the controller. That's the only one that is affected by the DCOMM button.

I can't explain what you are describing. I can only tell you what I know about the controller and software, based on my experience with them.

I am not sure if anyone will receive this, but I am going through similar issues. In my case, the OEM is using the MicroLogix 1200 Channel 0 port to communicate to a Maples HMI5043L. I am not able to communicate to the PLC at all with my computer no matter how I have my drive configured. The PLC is acting like it doesn't see my computer at all, meaning once I plug into the PLC using my Allen Bradley 9300-USBS. The comm light is not flashing at all when connected to my computer. I have the same issue with 2 other MicroLogix 1200's and have even tried different USB-Serial converter cables. The 9300-USBS cable is new as well. I am not sure what it is I am doing wrong, auto configuration doesn't work as well as manually entering the configuration settings. I have even tried the UIC DH485 driver as well to no avail. This is the first time that I have had to set up the RS-232 driver at my current job so I know I don't have to worry about a different port being used in the past and also I know that USB port does in fact work on my computer. I have tried all of the other ports on my computer as well.

Welcome to the PLCTalk forum community !

Let's take it one step at a time.

Press the DCOMM button and be sure the DCOMM LED comes on. The button is a well-hidden hardware button on the MicroLogix 1200 and 1500, and a LCD keypad function and indicator on the MicroLogix 1100 and 1400.

The connect your USB device and MicroLogix cable. Check the Windows Device Manager to verify what COM port number it is using.

Set an RSLinx Classic DF1 Full Duplex driver assigned to the correct Windows COM port. Use the default settings of 19200 baud, 8/N/1 framing, CRC error checking, SLC/MicroLogix device type.

If you've really designated the right COM port, and really set up the driver correctly, and really pressed the DCOMM button and put the MicroLogix in DCOMM mode, then if comms still doesn't work then it's likely you have a bad cable or damaged MicroLogix port.