Siemens AZL Modbus to AB Controllogix

[rajy2r]

I have a Siemens LMV52 with an AZL and am trying to read some values to display on an HMI. The PLC is an Allen Bradley Contrologix L81E.

Using the Modbus TCP Sample Code from Rockwell (TechNote: 470365), i would like to read via modbus.

Have a Moxa MB3170 unit as a convertor.

I made up a cable with the following connections between the AZL and Moxa as per the manual below using a cable with RJ45 on one end (AZL Com 2) and RS-232 on other (Moxa). AZL Manual Page 19, Moxa Manual Page 35

AZL Pin 1 to Moxa Pin 2
AZL Pin 3 to Moxa Pin 3
AZL Pin 4 to Moxa Pin 5

Siemens AZL Manual

Moxa MGate MB3170 Manual

I have tried to read values with Modscan 64 but it doesn't seem to work. Not sure if i am doing something wrong here.

Trying to get this step resolved before i can use the Modbus TCP Sample Code.

 

[kittydog42]

Your pinout looks correct. Here is a link to the most current manual for that product in North America, although your manual should be okay.

http://scccombustion.com/pdf/LMV5%20Tech%20Inst%20LV5-1000%20INDEXED%202018.pdf

I work for SCC, Inc. We distribute the product in North America, including Canada so I should be able to help you. First question: did you enable Modbus on the AZL? Here are some instructions copied from another document.

First, actvate the Modbus port on the AZL (no password required):
1. Operaton > OptgModeSelect > Type of Gateway = Modbus
2. Operaton > OptgModeSelect > GatewayBASin (older units GatewayDDCin)
3. The AZL should now read 'Gateway Mode active'.

Next, set up the required parameters through the AZL (no password required):
1. Params & Display > Access w-out PW > AZL > Modbus >
Address = 1 (or whatever you want)
2. Params & Display > Access w-out PW > AZL > Modbus > Baudrate = 19200 bit/s (or 9600 bit/s)
3. Params & Display > Access w-out PW > AZL > Modbus > Parity = no
4. Params & Display > Access w-out PW > AZL > Modbus > Timeout = 30s

Last, change the controller mode to allow Modbus operation (no password required):
1. Params & Display > Access w-out PW > LoadController > Confguration >
LC_OptgMode = IntLC Bus (only if you want to allow remote control, not needed for viewing data only)

There are also a lot of other caveats to reading Modbus on the LMV52. You can't read more than 20 consecutive registers. You have to start and end your read on a valid register. If a register spans more than one word such as a U32 or an array (date/time) or string, you must make sure you start at the beginning and/or don't end in the middle of the data. The addresses are written beginning at 0 so you may have to offset if your format is 40001-style. Lastly, if you make a mistake in the message it doesn't send an exception response - it just doesn't respond.

The best thing to do initially is see if you can use ModScan with an RS-232 serial port directly, bypassing the Moxa. Then you'll know the Modbus will respond. Sorry I can't help with the Moxa but I'd check that the serial port is wired right beyond the Tx/Rx/Gnd. Do you have to jumper the other pins? In your configuration, are you specifying the correct node ID to pass through or is that even required? I have used a TCP-RTU converter from Gridconnect but never Moxa.

Worst case scenario, if you wanted to send it (the Moxa, we have LMV52s...) to our office we could try to make it work and send it back to you with instructions. Send me a PM if that is what you want to do.