Collision detection in eia-485 bus systems
AssigneeABB Technology AG
InventorsCornelius HECKROTT, Henrik PIND
Life of this patent
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Abstract
A communication module is disclosed for Intelligent Electronic Devices (IEDs) which can implement the EIA-485 standard, including an intelligent hardware support that can allow a known software-based collision detection function to detect collisions independently of the location of the message sources on the transmission line. The hardware support can enable both a “strong signal driving” mode as well as a “weak signal driving” mode. In the weak mode, a biasing, or attenuating, or voltage-dividing resistor can be temporarily inserted between a transmitter, or voltage source, and the transmission line.
Claims15
A method of facilitating message collision detection in a communication bus system operating according to EIA-485, wherein a signal transmitter is connected to a transmission line for transmitting a binary signal including a first bit followed by a second bit, the method comprising:
- applying a first voltage indicative of the first bit to the transmission line;
- applying, during a transitional period shorter than a duration of the second bit, a second voltage indicative of the second bit to the transmission line;
- applying, during a weak driving period following the transitional period, a third voltage indicative of the second bit to the transmission line via a biasing resistor;
- and
- detecting a superposition of the third voltage with a signal from an interfering message source connected to the transmission line, by a receiver connected to the transmission line.
A communication module for an IED in a communication bus system operating according to EIA-485, comprising:
- a signal transmitter connectable to a transmission line for transmitting a binary signal including a first bit followed by a second bit, wherein the signal transmitter is configured to apply to the transmission line:
- a first voltage indicative of the first bit;
- during a transitional period shorter than a duration of the second bit, a second voltage indicative of the second bit;
- and
- during a weak driving period following the transitional period and via a biasing resistor, a third voltage indicative of the second bit.
A Substation Automation (SA) system, comprising:
- a plurality of Intelligent Electronic Devices (IEDs) connecting to a Station Bus and communicating according to DNP 3.0 via EIA-485, wherein each of the plurality of IEDs includes a communication module having a signal transmitter connectable to a transmission line for transmitting a binary signal including a first bit followed by a second bit, wherein the signal transmitter is configured to apply to the transmission line:
- a first voltage indicative of the first bit;
- during a transitional period shorter than a duration of the second bit, a second voltage indicative of the second bit;
- and
- during a weak driving period following the transitional period and via a biasing resistor, a third voltage indicative of the second bit.
Dependencies are inferred from the claim text.