Programmable logic controllers and the expression of relay ladder diagrams

摘要

A programmable logic controller checks each statement of an instruction list (IL) program to determine if any such statement or the order of statements violates one of a set of syntax rules which are stored in a memory in the controller. If a rule violation is found, an error indication is generated to signify that the particular IL program under test by the controller can not be accurately converted or translated into a relay ladder diagram. However, if no rule violation is found by the controller, then the controller accepts the IL program.