Programmable controller with a directed sequencer
US5042002A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 31, 1989 |
| Grant date | Aug 20, 1991 |
| Priority date | — |
| Expiry date | Mar 31, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05B19/058
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A programmable controller for sensing the status of input devices and controlling the state of operating devices in accordance with a stored ladder logic control program includes a step sequencer. A memory is provided for storing data regarding each step of the sequence. This data defines the operating device states for each step, and the legitimate transitions from that step to other selected steps in the sequence, along with the input status conditions which trigger a step transition. A processor responds to a ladder logic instruction by comparing the status of the input devices to the stored input status conditions for the current step to detect if a step transition should occur. Upon such a detection the sequencer advances to the step associated with the detected input status condition. Should an illegal transition from one step to another occur, an error message is generated. A step timer is also incorporated to force a transition when the sequencer remains at the same step longer than a defined period of time.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.