15ADVANCED LADDER LOGIC FUNCTIONS

Topics:

• Shift registers, stacks and sequencers

• Program control; branching, looping, subroutines, temporary ends and one shots

• Interrupts; timed, fault and input driven

• Immediate inputs and outputs

• Block transfer

• Conversion of State diagrams using program subroutines

• Design examples

Objectives:

• To understand shift registers, stacks and sequencers.

• To understand program control statements.

• To understand the use of interrupts.

• To understand the operation of immediate input and output instructions.

• To be prepared to use the block transfer instruction later.

• Be able to apply the advanced function in ladder logic design.

This chapter covers advanced functions, but this definition is somewhat arbitrary. The array functions in the last chapter could be classified as advanced functions. The functions in this section tend to do things that are not oriented to simple data values. The list functions will allow storage and recovery of bits and words. These functions are useful when implementing buffered and queued systems. The program control functions will do things that don’t follow the simple model of ladder logic execution - these functions recognize the program is executed left-to-right top-to-bottom. Finally, the input output functions will be discussed, and how they allow us to work around the normal input and output scans.

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