The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 21, 2002
Filed:
Sep. 14, 1998
Robert Charles Mason, Raleigh, NC (US);
Square D Company, Palatine, IL (US);
Abstract
A circuit for efficiently time-sharing the output and input configuration of a microprocessor I/O pin. The circuit includes a microprocessor having at least one I/O pin which can be selectively reconfigured for either output or input functions, a pull-up resistor, a dropping resistor and an output device. The pull-up resistor, dropping resistor and output device each have a common electrical connection at a terminal connected to the selected I/O pin. The pull-up resistor also has a terminal connected to the regulated power supply (Vcc) of the circuit. An input device or configuration switch, which is selectable between a first state and a second state, has one terminal connected to the dropping resistor and a second terminal connected to a point of the circuit at ground potential. The selected I/O pin is normally configured as an output pin for controlling the output device. At one or more intervals, as determined by a software program, the selected I/O pin will be reconfigured for input and will read the status of the input device. The input device will have provide a logical condition “1” or a logical condition “0” input status to the selected I/O pin depending on its selectable state of open or closed. The logical “1” or “0” is represented by a voltage level. The interval at which the selected I/O pin will be reconfigured for input is determined by both the type of output device being controlled and the type of input represented by the input device. The pull-up and dropping resistors have a resistance value ratio of 10:1 or greater. The actual resistance values are selected such that the output signal from the selected I/O pin can override the representative voltage levels of the logical conditions “1” or “0” of the input device when the selected I/O pin is configured for output.