Dual function input/output for a programmable controller
US4593380A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 4, 1984 |
| Grant date | Jun 3, 1986 |
| Priority date | — |
| Expiry date | Jun 4, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05B2219/21115
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
The invention disclosed provides circuitry which is selectively operable either as an input point or as an output point in a programmable controller having multiple input and output points for exchanging signals between a central processing unit (CPU) of the controller and a process being controlled. Preferably, operation as an input point or as an output point is under control of the CPU. The invention includes a common input/output terminal for terminating both input and output devices; an input return terminal for terminating a return conductor from the input device; an output return terminal for terminating a return conductor from the output device; a preload resistor connected between the input/output terminal and the output return terminal so that a status signal is developed across the preload resistor indicating the status (generally, open or closed) of the input device; and an insulated gate transistor (IGT) connected between the input/output terminal and the input return terminal. The insulated gate transistor, capable of being triggered on and off, is held in an off state whenever the circuit is selected to be operated as an input point and is triggered on and off when t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.