The Mitsubishi main communication module A1SJ51T64 offers highly configurable I/O capacity, supporting up to 128 points when using 8-point I/O combination modules. Alternatively, it allows for mixed use of arbitrary I/O modules, reaching a maximum of 64 points. This flexibility in system configuration ensures that each remote I/O component controls a sufficiently small number of I/O points, which helps avoid unnecessary waste of I/O capacity at the installation site of control equipment. Furthermore, the module provides significant installation flexibility without requiring terminal resistors or T-branch connections.

Structured Text (ST) is a programming language that uses structured, textual descriptions to define program logic. It resembles high-level programming languages and is commonly employed in large and medium-sized PLC systems to describe the relationships among various variables within a control system. ST is particularly useful for developing user programs that are difficult to implement using other programming languages.

Function Block Diagram (FBD) is a PLC programming language similar to digital logic circuits. It represents the functions of a program using graphical function blocks, where different blocks perform different operations. The key characteristics of FBD programming include its modular approach, which simplifies the analysis and understanding of control schemes. Since function blocks are expressed in graphical form, the language is highly intuitive and easy for designers with a background in digital logic circuits to learn. For large-scale control systems with complex logic, FBD clearly illustrates functional relationships, significantly reducing programming and debugging time.