DESIGN AND IMPLEMENTATION OF A NEW DATA TRANSMISSION PROTOCOL, SPI-RING PROTOCOL, CONNECTING TWO SINGLE MD100-PLC PROGRAMMABLE LOGIC CONTROLLERS VIA SPI INTERFACE TO FORM MODULAR MD100-PLC SYSTEM.

Abstract

In this paper, bi-directional data transmission protocol between two micro-controller boards connected via SPIInterface is presented. SPI-Ring Protocol is developed as a new transmission protocol for this purpose. In this connection, one of the controller acts as a master device while the other acts as a slave device. SPI-Ring protocol is mainly developed in order to connect two MD100-PLCs [MD100 Programmable Logic Controller]. Total I/O lines of the MD100-PLC become sometimes insufficient for the process under control. Connection of two MD100-PLCs forms modular MD100-PLC system having doubled I/O lines and suggests a reliably solution for the cases where the I/O lines of a single MD100-PLC are not adequate. The SPI-Ring Protocol is fully implemented in software for both master and server side devices in assembler language. Two test cases are created to test the SPI-Ring Protocol. Snapshots from the KUMANDA (The complete Program Development Environment for MD100 Programmable Logic Controllers developed in C++) showing the test programs are given. The programs are executed on the modular MD100-PLC system. States of the IO lines of the modular PLC-System are indicated in separate photos. The results have proven full satisfaction.