US 4,569,045 A · 3-Wire multiplexer

Abstract

The invention provides a 3-wire multiplexing system exhibiting high noise immunity, particularly suitable for industrial control applications. A master station provides AC power, and clocking and synchronization information, for a plurality of remote transmitter and receiver stations. A 3-wire cable links the master station and the remote stations. Two wires of the cable are power lines L1 and L2 and are isolated from each station by respective transformers. The third wire is a data line and is optically coupled to the remote stations. The remote stations are thus completely isolated from the cable, yet powered, clocked and synchronized therefrom without the need for local power supplies or local clocks. The signaling method switches the data line onto the power lines, and provides a high degree of data security by recognizing both the polarity and the position of a pulse on the data line within an AC cycle. The system further provides diagnostics in remote receivers including half cycle polarity and position decoding, error detection, fail state selection to fail OFF or fail ON or remain in the last valid state, and two scans alike detection.

Claims33

Dependent claims

A high noise immunity multiplexing system comprising:

a master station;
a plurality of remote stations;
and
a cable comprising three shielded wires linking said master station and said remote stations, two wires of said cable being power lines L1 and L2 for powering and for clocking said remote stations from said master station, such that said remote stations do not require local power supplies and do not require local clocks, a third wire of said cable being a data line, and further comprising a signaling system for carrying data comprising switching said data line into connection with said power lines in accordance with a given signaling format;
wherein said power lines carry AC power, and said signaling system comprises switching one of said AC power lines into connection with said data line at designated times;
wherein said signaling system uses one or more AC cycles per multiplex channel and provides data security by recognizing the polarity or the position, or both, of a pulse on said data line relative to an AC cycle.

3 more elements

A high noise immunity multiplexing system comprising:

a master station for generating power, clocking and synchronization signals;
a cable comprising three shielded wires, two of which are power lines linked to said master station, the third wire being a data line;
at least one remote transmitter station linked to said cable and including means synchronized by said synchronization signal and clocked by said clocking signal for connecting one of said power lines to said data line at a given addressed channel;
and
at least one remote receiver station linked to said cable and including means synchronized by said synchronization signal and clocked by said clocking signal for reading the state of said data line at a given addressed channel,
wherein:
said master station is linked to said power lines by transformer coupling means;
said remote transmitter station is linked to said power lines by transformer coupling means;
said remote transmitter station is linked to said data line by optical coupling means;
said remote receiver station is linked to said power line by transformer coupling means;
and
said remote receiver station is linked to said data line by optical coupling means.

9 more elements

A high noise immunity multiplexing system comprising:

(a) a master station outputting an AC waveform providing power and clocking, and periodically skipping one or more AC cycles at given intervals to set scan length and provide synchronization;
(b) a cable comprising three shielded wires, two of which are power lines transformer-coupled to said master station, the third wire being a data line;
(c) at least one remote transmitter station transformer-coupled to said power lines and comprising:
(i) sync detect means responsive to said AC waveform from said last mentioned transformer for detecting said skipped AC cycle;
(ii) address counter means responsive to said sync detect means and clocked by said AC waveform from said last mentioned transformer for generating an address valid output signal at a given addressed channel;
(iii) a sensor data latch responsive to said address valid signal for outputting sensor data;
(iv) transmit logic means responsive to said AC clocking waveform from said last mentioned transformer, and responsive to said address valid signal, and responsive to said sensor data latch, for emitting an optical actuation signal;
and
(v) transmit switch means responsive to said optical actuation signal for connecting one of said power lines to said data line;
and
(d) at least one remote receiver station transformer-coupled to said power lines and comprising:
(i) sync detect means responsive to said AC waveform from said last mentioned transformer for detecting said skipped AC cycle;
(ii) address counter means responsive to said last mentioned sync detect means and clocked by said AC waveform from said last mentioned transformer for generating an address valid output signal at a given addressed channel;
(iii) receive switch means for reading said data line, and including light emitting means emitting an optic signal in response to current flow on said data line;
and
(iv) decode logic means responsive to said optic signal for outputting the decoded logic state of said data line during said addressed channel.

13 more elements

Dependencies are inferred from the claim text.

3-Wire multiplexer

Life of this patent

3-Wire multiplexer

Life of this patent

Abstract

Claims33