Programmable logic controller
US3942158A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 24, 1974 |
| Grant date | Mar 2, 1976 |
| Priority date | — |
| Expiry date | May 24, 1994 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05B2219/1159
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A programmable controller includes a processor which executes a control program to alter the state of an output image table stored in a read/write memory in response to the state of an input image table stored in the memory. An input/output scanner circuit connects directly to the read/write memory and periodically steals a memory cycle from the processor to couple the status of input and output devices with corresponding bits in the input and output image tables. The rate at which the scanner circuit operates is independent of the processor speed and is selected to accommodate the input/output interface circuitry on the programmable controller.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.