Programmable controller with ladder diagram macro instructions

Abstract

A machine is operated by a programmable controller that executes a ladder logic control program. A custom ladder logic processor is provided for high speed execution of the more common ladder logic instructions and a microprocessor interprets the remaining ladder logic instructions. A first section of memory contains a ladder logic control program in which some of the instructions are macro instructions executable by the ladder logic processor. Each macro instruction specifies an operation code, a first memory file containing data to be processed by the macro instruction, a second memory file containing control data governing the processing, and a storage location for results produced by execution of the macro instruction. Another memory section stores a library file containing a ladder logic software routine for each macro instruction, and stores a directory which identifies a starting location of the macro instruction routine for each operation code. When a macro instruction is encountered in the control program, the corresponding ladder logic software routine is executed. During the execution of the routine data is obtained from the first memory file and the results are placed in the storage location. At the completion of the ladder logic software routine, execution of the control program resumes.