Gambit

1.create a project for an FX3U in GX Works 2. 2. Than setup your connection  3. Diagnostics - PLC Diagnostics  

No you cannot read the program, But you can read the error code (diagnostics)

That should work. But even though the program is  locked you should be able read the error code. Maybe the error can be solved without having to change hardware. could be a calculation error or something else

OK this is correct for checking the current status of the inputs. However your SCAN time will probably still be an issue. You should take this part of the program and add it to the time interrupt program.  (i28 i19 etc one which is fast enough)

In that case maybe your scan is just to long for operation. you should put this program into an interrupt program. Instead of using X51 for instance use DX51. (This way the current status is checked for the input and not the status at the start of the scan). Have you used interrupts before on a system Q?    

There are two thing to consider. Looks like this is part of your regular Scan program so it will only run every ..... ms But the second is probably the problem which is the amount of time your sensor is on. At higher speeds it's only on for less time. Your input would have a minimum time before it is seen as true (probably 10ms) Which PLC are you using ? So to change this you will have to change the Input Response time time of your Input card and maybe put this part of the program into an interrupt program. 

There are standard FB inside GX works 3 for modbus you can use. The SP open and close instruction just open and close the ports. But i guess the protocol is converted in the FB itself. So multiple connections should not be a problem.       

Are you using the pre-defined protocol function or the FB ?  

Appendix 9 https://dl.mitsubishielectric.com/dl/fa/document/manual/plcf/jy997d55401/jy997d55401n.pdf What sort of problems are you having with modbus

Which PLC ? Do you want to do by downloading it via software or via devices /HMI ?  

Really I had it working at a customer pretty quickly. As for the port Mitsubishi uses port 5000 and up for the own software. Kepware has a good document for making the connection(see attached)   mitsubishi-ethernet-manual.pdf

The kepware server support also the built in Ethernetport of the Q series CPU's. For UPC UA we use the Softec solution. https://www.ibhsoftec.com/epages/63444704.sf/de_DE/?ObjectPath=/Shops/63444704/Products/3200  I don not know if it ia available in the US, but there must be something similar    

 I agree with @panic mode I would also like to know the following . Do they need statistical  information to store in  Database or Real time data. What protocols are known on IT side like MQTT or OPC UA which is becoming more and more a standard.  

Hmm i think that woud be preference. I would do it in the HMI.  

Excellent. Do you need any help with the math issue ?