Abstract: A programmable controller has a rack that electrically connects a number of I/O modules to a processor module. The processor module includes a external device communication interface section and a general purpose processor section electrically coupled together by a set of common buses. Both of these module sections include a microprocessor and memory connected by an internal set of buses which are isolatable from the set of common buses. The isolation capability permits the different sections to perform their operations simultaneously. A shared system memory and an rack interface are coupled to the common buses for the exchange of data with the I/O modules. A unique ladder logic processor also is connected directly to the common buses. The ladder logic processor includes a hardwired Boolean bit logic processor and a custom microcoded processor to execute instructions of a ladder type control program.

Abstract: A programmable controller stores a user control program which is comprised of a plurality of conventional ladder programs and a structure chart program. A microprocessor executes a structure chart interpreter routine to interpret the structure chart program and to thereby create an active state list which indicates the ladder programs that are to be executed. The same microprocessor with the assistance of a bit processor also executes the ladder programs which are indicated on the active state list to control a machine connected to the programmable controller.

Abstract: A programmable controller includes a memory which stores an I/O image table and a data table. An I/O scanner module updates the I/O image table with the status of I/O devices connected to the programmable controller. The processor executes a control program to perform logical and arithmetic operations on the data in the data table. Such operations may be performed on data of different types and any necessary data conversions are performed automatically. Also, such operations may be performed on entire data files without degrading the response time of the programmable controller.