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I recommend trying to get the UC300 to communicate to your computer running a Modbus slave simulator, such as ModSim. Setup just a single register and confirm communications. ModSim, and many other slave simulators, can also show the traffic so you will be able to definitively confirm that you...

Yes, you have the right idea. You will need to perform a read, modify, write procedure on the UPS_CONFIG (0x00D2) register. First, read the value using the 0x03 Read Holding Registers command. The value read will be 16 bits. Modify the bit you'd like to change in the value, then write the...

First off, you're not trying to read data from this Modbus slave with the UC300 while it is still connected to the wise-5800 master are you? Modbus RTU allows only one master. What makes you believe the Slave ID in the UC300 must be entered in hexadecimal? From the user's guide...

An exception response means that the device is responding with an error code. However, the fact that the device is responding (even though it is an exception code) does mean that your communication settings (baud rate, parity, address, etc.) are correct. You are probably accessing registers...

According to the manual, it seems you must have a Modbus master, such as ModScan (in conjuction with a standard USB to RS-485 adapter or optionally VP Instrument's proprietary USB cable), to configure the communication settings on the sensor. Its default communication settings are as follows...

What is the vendor and model of the sensor? Do you have a users manual, communication manual, or similar? There are 3 typical ways a Modbus slave device is configured Using a display and menu system built into the product Using a proprietary software tool provided by the vendor on your...

Sorry, my mistake. I saw the E and went straight to FR-E800, not E meaning the Ethernet version of the A800. However, from a communication standpoint, I believe the F, A, and E drives are all nearly identical, so everything I said previously applies to all 3 types of 800-series drive. Here are...

The registers you must write to in order to run/stop and control the frequency of the VFD via Modbus/TCP can be found in the FR-E800 Instruction Manual (Communication) https://dl.mitsubishielectric.com/dl/fa/document/manual/inv/ib0600871eng/ib0600871engl.pdf Page 100 details the relevant...

While the overall concept of the solution you've presented makes sense, there is a lot of seemingly incorrect information here. I know you and David_2 already talked about this, but again, there is no such thing as "null" in Modbus. Also, as you stated, the ProSoft can't be writing a zero...

What is the USB to RS-485 converter you're using? Does it have any type of "echo" settings on it that may be causing it to send each request character back to the laptop?

A new, unmanaged switch will not function like an old hub. It will only send packets to the specific port(s) necessary. You cannot perform capturing using Wireshark with an unmanaged switch, since you cannot enable port mirroring. You need to use a managed switch that supports port mirroring or...

Good observations. So it seems that the Prosoft may be creating new TCP connections for writes. Have you asked Prosoft about this behavior? Is this expected? Unless your "hub" is 20 years old or is a very specialized modern device, it is more than likely a standard switch and will not send all...

Interesting. So are the 3 Maxcess units that use the FL BT EPA bridges the ones you mentioned in your original post that drop out after a few days and the one that lasts a week or two is the one without the FL BT EPA bridge? Do any other devices on this network use a FL BT EPA bridge? Perhaps...

A web search tells me the following: The DT80 supports both Modbus/TCP and Modbus RTU (via RS-232, RS-422 or RS-485) The Freewave FGR-2 seems to only support serial ports. However, the FGR2-P and FGR2-PE have both serial ports and Ethernet ports. The 200-PEU seems to be a device made by...

FWIW, I don't know that I'd necessarily trust the information provided by the Maxcess devices, since they're the devices having issues, possibly due to a firmware bug. It is not unreasonable to assume that information provided by these devices is untrustworthy. It would be best to verify this...

How did you determine the ProSoft card created several concurrent TCP connections? Did you capture the Ethernet packets using Wireshark? Similarly, how did you determine this is what's causing the lockups? Assuming you took a capture, does the Wireshark capture show the Maxcess devices...

I'm not familiar with the configuration settings on that switch, but whatever configuration you can do with the Stratix switch to make it operate as close to a dumb, unmanaged switch as possible for that port will probably be your best bet in getting the Maxcess devices to behave.

Having the devices on a VLAN, in general, is not problematic. The issue is the meta data (e.g. encapsulation) added to the Ethernet frames by the switch. If the Stratix's VLAN port that is connected to the TPLink switch is configured as "tagged" (a.k.a. a "trunked port"), then the switch will...

The details you've provided (adding now that rebooting the TPLink switch does not resolve the issue) continue to seem point to a firmware issue with the Maxcess devices. I do, however, still recommend performing the test I mentioned in my last post to confirm that, even when directly connected...

The fact that pings and ARP still work but HTTP (port 80) and Modbus (port 502) stop working leads me to believe this is a firmware bug in the Maxcess devices. Unfortunately, intermittent issues such as this are very hard for manufacturers to debug and fix, especially if they are unable to...