I already created the tags for my PLC in VTScada. I am trying to pull the digital status of a device in my system. First I was using Y memory bit, the digital status can be pulled correctly, I can see a value 1 shown on the Tag when that device was on. The Y memory bit address and function code are attached.

Then, I changed the Y memory to C memory bit, the device is still working well. However, after I change the Modbus address to the specific C memory bit, VTScada can no longer read the digital status of the device. There is no number appear on the value column. I attached a picture of my PLC Modbus address and function code for C memory bit below:

The VTScada was shown nonthing, the picture was attached:

Anyone know what is the reason that I cannot pull the digital status of the C memory bit?

Really appreciate any help!

Not sure how your PLC and Software translates that "Y" and "C" codes into Modbus registers. You'd probably have better luck reaching out to the software vendor for your PLC software so you know how they translate into standard modbus register locations.

Object type             Access       Size        Address Space
Coil                  Read-write     1 bit       00001 - 09999
Discrete input        Read-only      1 bit       10001 - 19999
Input register        Read-only      16 bits     30001 - 39999
Holding register      Read-write     16 bits     40001 - 49999