Where can I find the function of mod bus of delta dvp to connect to visual basic 2008?

Dear, Modbus is about reading registers values by calling them by thier addresses. So you have to find a dll library (or u can design your own) which work on your required interface and connect to delta dvp plc then use thier protocol to read registers.

u can find info about thier modbus protocol in below link.

file:///C:/Users/HASEEB/Downloads/DVP_%20communication%20Protocol.doc