Pre-scaler for orthogonal differential vector signalling
Orthogonal differential vector signalling (ODVS) techniques are described. The ODVS encoding schemes described herein generate one sub-channel for each bit by multiplying each bit by a different row in a transmitter encoding matrix to produce a set of sub-channels. Each wire carries a signal that is a superposition of elements from all of the sub-channels in the set. The transmitter encoding matrix is selected such that its rows (i.e. sub-channels) are mutual orthogonal. This means that the receiver can decode the signals received from all wires in concert to reliably recover the original bits. The transmitter encoding matrix applies weights to each sub-channel of the set, with the absolute magnitude of the weights decreasing as the number of wires associated with the respective sub-channel increases.
1. A communication system comprising:
a multi-wire communication link having eight wires;
an orthogonal differential vector signalling encoder configured to receive a set of seven input bits and to responsively generate a set of symbols of a codeword of a vector signalling code, the codeword corresponding to a weighted summation of a plurality of sub-channel vectors that correspond to rows of a transmitter encoding matrix, wherein each of the sub-channel vectors has a plurality of non-zero elements, each of the plurality of non-zero elements respectively corresponding to one of the eight wires, wherein four of the plurality of sub-channel vectors are pair sub-channel vectors, each pair sub-channel vector associated with only a respective two of the eight wires and having a common first absolute magnitude weighting, two of the plurality of sub-channel vectors are tetrad sub-channel vectors associated with only a respective four of the eight wires and having a common second absolute magnitude weighting that is lower than the first absolute magnitude weighting, and one of the plurality of sub-channel vectors is an octad sub-channel vector associated with all of the eight wires and having a third absolute magnitude weighting that is lower than the first absolute magnitude weighting and lower than the second absolute magnitude weighting; and
a set of drivers configured to transmit each symbol of the codeword over a respective wire of the multi-wire communication link by driving the respective wire with a wire signal level.
2. The communication system of claim 1 wherein each pair sub-channel vector is associated with a respective pair of physically adjacent wires of the eight wires.
3. The communication system of claim 1 wherein each tetrad sub-channel vector is respectively associated with two pairs of wires of the eight wires, the two pairs of wires arranged physically adjacent one another and each pair of the two pairs of wires comprising two physically adjacent wires.
4. The communication system of claim 1 wherein for each sub-channel vector of the plurality of sub-channel vectors, one half of the wires associated with the respective sub-channel vector have associated non-zero elements that have an equal magnitude but an opposite sign to non-zero elements associated with the other half of the wires associated with the respective sub-channel vector.
5. The communication system of claim 1 wherein each wire of the eight wires is associated with one pair sub-channel vector, one tetrad sub-channel vector and one octet sub-channel vector.
6. The communication system of claim 1 wherein each wire of the eight wires is associated with elements of only three sub-channel vectors of the plurality of sub-channel vectors.
7. A method, comprising:
receiving a set of seven input bits at an orthogonal differential vector signalling encoder coupled to a multi-wire communication link having eight wires;
responsively generating, by the orthogonal differential vector signalling encoder, a set of symbols of a codeword of a vector signalling code, the codeword corresponding to a weighted summation of a plurality of sub-channel vectors that correspond to rows of a transmitter encoding matrix, each of the sub-channel vectors having a plurality of non-zero elements, each of the plurality of non-zero elements respectively corresponding to one of the eight wires, wherein four of the plurality of sub-channel vectors are pair sub-channel vectors associated with only a respective two of the eight wires and having a common first absolute magnitude weighting, two of the plurality of sub-channel vectors are tetrad sub-channel vectors associated with only a respective four of the eight wires and having a common second absolute magnitude weighting that is lower than the first absolute magnitude weighting, and one of the plurality of sub-channel vectors is an octad sub-channel vector associated with all of the eight wires and having a third absolute magnitude weighting that is lower than the first absolute magnitude weighting and lower than the second absolute magnitude weighting; and
transmitting, by a set of drivers, each symbol of the codeword over a respective wire of the multi-wire communication link by driving the respective wire with a wire signal level.
8. The method of claim 7 wherein each pair sub-channel vector is associated with a respective pair of physically adjacent wires of the eight wires.
9. The method of claim 7 wherein each tetrad sub-channel vector is respectively associated with two pairs of wires of the eight wires, the two pairs of wires arranged physically adjacent one another and each pair of the two pairs of wires comprising two physically adjacent wires.
10. The method of claim 7 wherein for each sub-channel vector of the plurality of sub-channel vectors, one half of the wires associated with the respective sub-channel vector have associated non-zero elements that have an equal magnitude but an opposite sign to non-zero elements associated with the other half of the wires associated with the respective sub-channel vector.
11. The method of claim 7 wherein each wire of the eight wires is associated with one pair sub-channel vector, one tetrad sub-channel vector and one octet sub-channel vector.
12. The method of claim 7 wherein each wire of the eight wires is associated with elements of only three sub-channel vectors of the plurality of sub-channel vectors.
13. A communication system comprising:
a multi-wire communication link having eight wires;
an orthogonal differential vector signalling encoder configured to receive a set of seven input bits and to responsively generate a set of symbols of a codeword of a vector signalling code, the codeword corresponding to a weighted summation of a plurality of sub-channel vectors that correspond to rows of a transmitter encoding matrix, wherein each of the sub-channel vectors has a plurality of non-zero elements, each of the plurality of non-zero elements respectively corresponding to one of the eight wires, wherein four of the plurality of sub-channel vectors are pair sub-channel vectors having non-zero elements associated with only two of the eight wires and each pair sub-channel vector is associated with a respective pair of physically adjacent wires of the eight wires, two of the plurality of sub-channel vectors are tetrad sub-channel vectors having non-zero elements associated with only four of the eight wires, and one of the plurality of sub-channel vectors is an octad sub-channel vector having non-zero elements associated with all of the eight wires, wherein, for a given sub-channel vector of the plurality of sub-channel vectors, each of the plurality of non-zero elements of the given sub-channel vector has a common absolute magnitude; and
a set of drivers configured to transmit each symbol of the codeword over a respective wire of the multi-wire communication link by driving the respective wire with a wire signal level.
14. The communication system of claim 13 wherein all of the pair sub-channel vectors have non-zero elements with a common absolute magnitude.
15. The communication system of claim 13 wherein each tetrad sub-channel vector is respectively associated with two pairs of wires of the eight wires, the two pairs of wires arranged physically adjacent one another and each pair of the two pairs of wires comprising two physically adjacent wires.
16. The communication system of claim 15 wherein all of the tetrad sub-channel vectors have non-zero elements with a common absolute magnitude.
17. The communication system of claim 13 wherein for each sub-channel vector of the plurality of sub-channel vectors, one half of the wires associated with the respective sub-channel vector have associated non-zero elements that have an equal magnitude but an opposite sign to non-zero elements associated with the other half of the wires associated with the respective sub-channel vector.
18. The communication system of claim 13 wherein each wire of the eight wires is associated with one pair sub-channel vector, one tetrad sub-channel vector and one octet sub-channel vector.
19. The communication system of claim 13 wherein each wire of the eight wires is associated with elements of only three sub-channel vectors of the plurality of sub-channel vectors.