Prosoft PX51 PBM

If anyone has any experience using this product as a profibus slave and modbus tcp master setup to PCS7 300 series processor. Receiving data but only for the first 8 registers from modbus to the input words. Data is from modbus holding registers. All the received data is correct and in the expected place. Just not beyond the first eight.
 
Modbus registers are 2 bytes each. Using a 16-byte input module could explain why you're only seeing 8 registers. You may need to use a 32 byte input module to see 16 Modbus registers.

Have you mapped 16 Modbus Holding Registers per slot or 16 in total (presumably 8 per slot)?
 
Modbus registers are 2 bytes each. Using a 16-byte input module could explain why you're only seeing 8 registers. You may need to use a 32 byte input module to see 16 Modbus registers.

Have you mapped 16 Modbus Holding Registers per slot or 16 in total (presumably 8 per slot)?
16 registers total. Eventually it will be 44.
 
Let's try to determine if the problem lies between your PROFIBUS master and the PLX51-PBM or if the problem is between the PLX51-PBM and your Modbus server device.

You stated, "Receiving data but only for the first 8 registers from modbus to the input words. All the received data is correct and in the expected place. Just not beyond the first eight."

Where exactly are you seeing this? In your PROFIBUS master? Is the PROFIBUS master the PCS7 300 series processor? What do you see beyond the first 8 registers? Are values shown, just perhaps a value of 0 when you expect it to be non-zero?

Maybe the PLX51-PBM's Modbus requests are failing for the registers after the first 8. I recommend downloading a Modbus master simulator such as ModScan, Simply Modbus, Modbus Poll, etc. and try reading the exact Holding Registers you are trying to access using the PLX51-PBM. You want to check to see if you're getting any errors when reading these registers. Make sure you're register numbering is consistent and is using either 0-based or 1-based (the number used by PLX51-PBM depends on the Base Offset Type setting under the Modbus Addressing configuration tab).
 
I am seeing the data in the Profibus master using a variable table. The first 8 are populated with the correct data and the next eight are zeros. Modpoll reads all the registers being sent. I am using the “PLC base 1” setting.
 
Is the variable table a table of tags that you created or is it the raw I/O data array? If it is tags, is it possible for you to monitor the raw input data array?

From reading the PLX51-PBM's manual, it doesn't seem that gateway has any diagnostics features that would allow you to confirm that it is successfully reading the Modbus data or what data is being exchanged on the PROFIBUS connection. If you haven't done so already, you may need to contact Prosoft technical support for assistance in troubleshooting this issue.

The only other thing I can think of to do is use Wireshark to capture the Modbus/TCP traffic to confirm that the PLX51-PBM is sending requests for all expected registers and that the Modbus server device is responding with a successful response. In order to do this, though, you will need an Ethernet switch that has port mirroring or use an Ethernet tap device.
 
Is the variable table a table of tags that you created or is it the raw I/O data array? If it is tags, is it possible for you to monitor the raw input data array?

From reading the PLX51-PBM's manual, it doesn't seem that gateway has any diagnostics features that would allow you to confirm that it is successfully reading the Modbus data or what data is being exchanged on the PROFIBUS connection. If you haven't done so already, you may need to contact Prosoft technical support for assistance in troubleshooting this issue.

The only other thing I can think of to do is use Wireshark to capture the Modbus/TCP traffic to confirm that the PLX51-PBM is sending requests for all expected registers and that the Modbus server device is responding with a successful response. In order to do this, though, you will need an Ethernet switch that has port mirroring or use an Ethernet tap device.
Thanks I will give all that a try!
 
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