Programmable Logic Controllers, 5th Edition

Chapter 6. IL, SFC, and ST Programming Methods

This chapter continues from the previous chapter and discusses the other IEC 1131-3 programming languages, that is, instruction lists (ILs), sequential function charts (SFCs), and structured text (ST).

6.1. Instruction Lists

A programming method that can be considered to be the entering of a ladder program using text is the instruction lists (IL). An instruction list gives programs as a series of instructions, with each instruction on a new line. Each instruction consists of an operator followed by one or more operands, that is, the subjects of the operator. Thus we might have:

to indicate that the operand ...