Dynamically changing the logical behavior of the microcomputer interface

Industrial programmable controllers and hardware simulators currently use the software method of direct logic simulation. In this method, programs contain the logical functions of several Boolean variables that are encoded directly. Each combinational circuit expressed by a group of Boolean equations requires an independent program. An alternative solution for the software implementation of the Boolean equations, named the product terms method, is presented. This method features the use of a single program to implement any multiple-output combinational circuit. To make the distinction between different circuits, a block of data defines each circuit. The product method is extended to synchronous sequential circuits, for which two tables are used. One table determines the next state of the combinational circuit, and the second table determines the outputs. An expert system has been developed to generate the table used in the product terms by interpreting the symbolic Boolean equations supplied by the user. The implementation and testing of the method are described.<>