Communications system for driving pairs of twisted pair links
First Claim
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1. A communications system comprising:
- a first high speed link having a first transformer interface at a transmit end and a second transformer interface at a receive end;
a second high speed link having a third transformer interface at a transmit end and a fourth transformer interface at a receive end;
a low speed link comprising a phantom circuit formed by the first to fourth transformers, the transmit end of the low speed link being formed by connections to the centre taps of the first and third transformers and the receive end of the low speed link being formed by connections to the centre taps of the second and fourth transformers;
wherein the transmit end of the low speed link is connected to a power supply and wherein the transmit end of the low speed link comprises a switch for periodically interrupting the power supplied from said power supply, at least one of the high speed links being connected to a device at the receive end for receiving signals from the respective high speed link, the receive end of the low speed link being capable of providing power and signals to the device from the power supply.
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Abstract
A communication system includes two high speed communication links formed by pairs of transformers at either end thereof. A phantom circuit formed by the pairs of transformers is used to distribute power to devices connected to the high speed links. In transmission part of a communications system, data is transmitted under the control of a continuously variable frequency clock. Transmission is on parallel data-strobe links, and the receive includes circuitry to identify on which parallel the data signal is preset. A method and circuitry is provided for transmitting and receiving dc balanced data strobe signals.
119 Citations
26 Claims
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1. A communications system comprising:
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a first high speed link having a first transformer interface at a transmit end and a second transformer interface at a receive end; a second high speed link having a third transformer interface at a transmit end and a fourth transformer interface at a receive end; a low speed link comprising a phantom circuit formed by the first to fourth transformers, the transmit end of the low speed link being formed by connections to the centre taps of the first and third transformers and the receive end of the low speed link being formed by connections to the centre taps of the second and fourth transformers; wherein the transmit end of the low speed link is connected to a power supply and wherein the transmit end of the low speed link comprises a switch for periodically interrupting the power supplied from said power supply, at least one of the high speed links being connected to a device at the receive end for receiving signals from the respective high speed link, the receive end of the low speed link being capable of providing power and signals to the device from the power supply.
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2. A communications interface comprising:
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output circuitry for providing two parallel outputs, one in the form of a data signal and one in the form of a strobe signal and including strobe generation circuitry, wherein the data signal comprises a serial bit pattern and the strobe generation circuitry generates the strobe signal such that the strobe signal has signal transitions only at bit boundaries where there is no transition on the data signal, the strobe generation circuitry being controlled by a clock signal such that for each clock pulse where there is no signal transition in the data signal a signal transition is generated in the strobe signal, the frequency of the clock signal being continuously variable; and input circuitry having two inputs for receiving data and strobe signals, and including an exclusive-or circuit for receiving the data and strobe signals and generating a receive clock on the output thereof, the receive clock being generated with clock signal transitions having a timing matching that at which the strobe and data signals were transmitted.
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3. Data receiving circuitry comprising:
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input circuitry having two inputs, one input for receiving a data signal and the other input for receiving a strobe signal, the strobe signal being parallel to the data signal and having signal transitions only at bit boundaries where there is no transition on the data signal; an exclusive-or gate, having inputs connected to the two inputs, and generating a receive clock on the output thereof; detection circuitry having two inputs coupled to the respective two inputs of the input circuitry and for detecting an expected bit sequence associated with the data signal on one of said two inputs; output circuitry for outputting the data signal under the control of the receive clock; and selection circuitry for connecting the one of said inputs on which said sequence is detected to the output circuit.
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4. A method of establishing parallel data and strobe signal communication paths having dc balanced data and strobe signals on each path, comprising:
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generating a binary data signal comprising signal level transitions at predetermined bit boundaries; generating and supplying a binary strobe signal, parallel to the binary data signal, having signal transitions at bit boundaries other than said predetermined bit boundaries on the parallel binary data signal; and encoding the binary data signal into a ternary data signal and the binary strobe signal into a ternary strobe signal, each said ternary signal comprising a sequence of trits and being dc balanced for transmission, wherein the step of encoding the binary data signal and the binary strobe signal into respective ternary dc balanced signals encodes such signals such that only single level logic transitions are permitted between successive trits of the ternary signals. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Data transmission circuitry comprising:
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input circuitry for receiving a binary data signal, said binary data signal comprising signal level transitions at predetermined bit boundaries; strobe generation circuitry for generating a binary strobe signal, parallel to the binary data signal, and having signal transitions at bit boundaries other than said predetermined bit boundaries on the parallel binary data signal; encoding circuitry for encoding the binary data signal into a ternary data signal and the binary strobe signal into a ternary strobe signal, wherein said ternary signals each comprise a sequence of trits and are dc balanced; and output circuitry for transmitting the ternary encoded data and strobe signals, wherein the input circuitry receives n binary bits to be transmitted and further comprises; bit generation circuitry for generating a flag bit associated with the n binary bits; addition circuitry for adding the flag bit to the n binary bits to form a binary code-word; calculation circuitry for calculating the running digital sum of successively formed binary code-words; inversion circuitry for inverting the n binary bits of data in a code-word in dependance on the current running digital sum and for setting the flag bit to indicate inverted data; and outputting as the binary data signal successive code-words. - View Dependent Claims (17, 18, 19, 20)
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21. A method of decoding a ternary data signal and a parallel ternary strobe signal, said ternary data signal comprising a sequence of trits and carrying data comprising signal carrying timing information comprising signal level transitions at predetermined trit boundaries, said ternary strobe signal level transitions at trit boundaries other than said predetermined trit boundaries, the method comprising:
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rectifying the ternary data signal into a binary data signal and the ternary strobe signal into a binary strobe signal; exclusive-ORring the binary data and binary strobe signals to generate a receive clock signal; and outputting the binary data signal under the control of the receive clock signal, wherein the ternary data signal comprises a plurality of code-words including a flag bit indicative of whether the data in the code-word is inverted or non-inverted, and further comprises the steps of; inverting or not inverting the data in the received code-word in dependance on the flag bit of the code word. - View Dependent Claims (22)
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23. Data receiving circuitry comprising:
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input circuitry for receiving a ternary data signal and a parallel ternary strobe signal, said ternary data signal comprising a sequence of trits and carrying data comprising signal level transitions at predetermined trit boundaries, said ternary strobe signal carrying timing information comprising signal level transitions at trit boundaries other than said predetermined trit boundaries; rectification circuitry for rectifying the ternary data signal into a binary data signal and the ternary strobe signal into a binary strobe signal; an exclusive-OR gate for receiving the binary data and binary strobe signals and generating a receive clock signal at its output; and output circuitry for outputting the binary data signal under the control of the receive clock signal, wherein the received ternary data signal comprises code-words including ternary trits and a flag trit, the data receiving circuitry further comprising control means for receiving the flag trit and in dependance thereon inverting or not inverting the bits of data in the received code-word. - View Dependent Claims (24, 25, 26)
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Specification