US 5,684,826 AGranted

RS-485 multipoint power line modem

AssigneeACEX Technologies, Inc.

InventorBoris Ratner

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Abstract

A modem enabling multi-point networks to be established over power lines emulating the RS-485 electrical interface standard for data transmissions. The modem includes a data terminal interface unit for exchanging data with a data terminal, a power line interface unit for placing data onto and taking data off of the power line, and a parallel I/O interface connecting the two units and including a network processor implementing a network protocol for sending and receiving messages. The parallel I/O interface provides for very fast data transfers across the parallel I/O interface compared with the rates at which the modem receives data from the power line and from the data terminal. In addition, at least the outgoing data is transferred across the parallel I/O interface in a form intermediate between the serial RS-485 data stream from the data terminal and the message packet that is sent over the power line by the power line interface unit. The parallel I/O interface facilitates reliable and flexible transfers compensating for delays and uncertainties in the transmission rate over the power line.

Claims6

Dependent claims

Apparatus for interfacing a plurality of data terminals over a power line for the exchange of data, said data terminals sending and receiving data according to the RS-485 electrical interface standard, comprising:

a data terminal interface portion for receiving and sending a serial RS-485 data stream from and to a first of said data terminals at a first nominal data rate, said serial RS-485 data stream comprising a plurality of data bytes;
a power line interface portion for receiving data from and sending data to said power line at a second nominal data rate;
and
a parallel I/O interface connecting said data terminal interface portion with said power line interface portion for communicating data back and forth therebetween;
wherein said parallel I/O interface comprises:
a network processor implementing a network protocol for sending and receiving messages over said power line through said power line interface portion;
outgoing data transfer means for transferring said plurality of data bytes from said data terminal interface portion to said network processor in an intermediate form at an internal transfer rate substantially greater than said first and second nominal data rates for inclusion in an outgoing message to be passed to said power line interface portion;
and
incoming data transfer means for transferring the data in an incoming message received from said power line interface portion to said data terminal interface portion at said internal transfer rate to be passed to said first data terminal as an RS-485 data stream;
whereby said apparatus emulates an RS-485 communications environment for said plurality of data terminals.

7 more elements

A method of interfacing a plurality of data terminals over a power line for the exchange of data, said data terminals sending and receiving data according to the RS-485 electrical interface standard, comprising the steps of:

providing a network processor implementing a network protocol for sending and receiving messages over said power line, said messages being sent and received over said power line at a first nominal data rate;
receiving a serial RS-485 data stream from a first of said data terminals at a second nominal data rate;
converting said serial RS-485 data stream to a parallel data stream;
feeding said parallel data stream to a first buffer;
forming a first packet from the data in said first buffer as of a prescribed time;
transferring said first packet to a second buffer at a rate substantially greater than said first and second nominal data rates while continuing to feed said parallel data stream to said first buffer;
retrieving said first packet from said second buffer and forming a second packet therefrom, said second packet including data from said first packet and additional network routing data;
transmitting said second packet over said power line according to the protocol of said network processor to at least one other of said data terminals;
and
successively repeating said steps of forming a first packet, transferring said first packet, retrieving said first packet and forming said second packet, and transmitting said second packet until all of said serial RS-485 data stream has been transmitted.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/590,035Filed 8 Feb 1996
Granted: 4 Nov 1997
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04B 3/542
Systems for transmission via power distribution lines: the information being in digital form
H04L 25/45
Transmitting circuits; Receiving circuits: using electronic distributors
H04B 2203/5408
Methods of transmitting or receiving signals via power distribution lines: using protocols
H04B 2203/5425
Methods of transmitting or receiving signals via power distribution lines: improving S/N by matching impedance, noise reduction, gain control