Why does the 1010 use SLIP protocol and not Modbus?
Modbus is a register based protocol and it is good for transmitting a process variable such as a total or temperature. Such variables are sent by addressing the register and requesting the value in that register to be sent. In the case of a product total, the value may be stored in four successive registers. Consequently, all four register values must be requested and the results must then be reconstructed in the computer.The advantage of Modbus is that it has a well defined instruction set and most PLC and SCADA systems have interface drivers built-in.However, the standard version of Modbus is not designed to transfer large amounts of information or information that has a variable length. For this application a packet based protocol is far more efficient.The protocol used in the Model 1010, SLIP, is a packet based protocol with a well defined structure and in-built error checking. It was originally used in the internet, prior to the PPP protocol that is common today.
