Programmable logic controller

Details Programmable logic controller Programmable logic controller

1974-05-24

1976-03-02

Malzahn, David H.

Communications: electrical

Digital comparator systems

G06F 700, G06F 906

Patent

active

039421589

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.

REFERENCES:
patent: 3624611 (1971-11-01), Wirsing
patent: 3651484 (1972-03-01), Smeallie
patent: 3731279 (1973-05-01), Halsall et al.
patent: 3827030 (1974-07-01), Seipp

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