Series port connection of a plurality of terminals to a master p

Details Series port connection of a plurality of terminals to a master p Series port connection of a plurality of terminals to a master p

1986-01-27

1988-02-16

Yusko, Donald J.

Communications: electrical

Continuously variable indicating

With meter reading

340825520, 370 85, 375 36, H04Q 900, H04J 300

Patent

active

047258365

ABSTRACT:
A circuit arrangement for connecting a plurality of digitally operated terminals to a single communications circuit of a master digital processing unit, such as a central computer, for transmission of information therebetween. The circuit comprises a first data bus for delivery of information from the processing unit to the terminals and a second data bus for delivery of information from each of the individual terminals to the central processing unit. A connecting circuit connects each of the individual terminals to the buses in a series arrangement such that each of the terminals are serially connected to the central computer through the single central port thereof. A line isolation circuit is associated with each of the terminals and comprises a diode in the output line of that terminal to enable data on the second of the buses to maintain a certain signal level and to prevent any other terminal, serially connected to the buses, from simultaneously drawing down the voltage level of the signal being transmitted to the central terminal. A pull-down resistor is also connected to one or more of the terminals to reduce the voltage level on that bus when data delivery has been completed. This circuit arrangement is especially useful for the RS-232 communication circuit format.

REFERENCES:
patent: 4086534 (1978-04-01), Olson
patent: 4403111 (1983-09-01), Kelly
patent: 4534038 (1985-08-01), Dodds
patent: 4547879 (1985-10-01), Hamelin et al.
patent: 4597076 (1986-06-01), Bingham et al.
patent: 4601030 (1986-07-01), Croiser
patent: 4607379 (1986-08-01), Marshall, Jr. et al.
patent: 4621367 (1986-11-01), Horiguchi et al.
patent: 4628308 (1986-12-01), Robert
patent: 4636790 (1987-01-01), Diamond
patent: 4654655 (1987-03-01), Kowalski

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