Executing downloaded user programs in a programmable controller

摘要

A program in a higher-level language for a programmable controller is stored as a hex-coded file in a memory in a main processor unit. The file is downloaded to a processor-based I/O logic module that translates the program into a multi-table data structure for relating the state of output devices on controlled equipment to the state of input devices on the equipment. After translation, an I/O control routine of lower-level, machine-language processor instructions is executed every 500 microseconds to control the output devices in response to changing conditions at the input devices and in response to the output functions embedded in the data structure as a result of translating the downloaded program. In a first embodiment the higher-level language is of the ladder-diagram type, while in a second embodiment the higher-level language incorporates state transition logic.