Digital controller display

Claim 1

A digital controller comprising: means for receiving analog signals indicating process variables of a process; means for converting said signals to digital form; a microprocessor for calculating a manipulated variable by arithmetic operations in accordance with a predetermined algorithm to cause the process variable signal to follow a setpoint variable; an operation data output system for delivering an output for controlling the process, said system having means for holding the manipulated variable received from the microprocessor and manually operable if said microprocessor fails; bar graph display type electronic indicating means for displaying the process variable, the setpoint variable, and the manipulated variable; and driver means including control circuit means for outputting control signals and clock signals to control the timing of operation of said driver means, two registers for receiving the process variable and the setpoint variable from the microprocessor, said two registers selectively outputting the process variable and the setpoint variable in response to signals from the microprocessor, counter means for counting said clock signals output from said control circuit means, and selective drive means for furnishing selective drive signals to said bar graph display type electronic means in response to said control signals from said control circuit means said driver means further acting to receive the manipulated variable from the holding means of the operation data output system for driving the electronic indicating means.