Methods and systems for noise resilient, pin-efficient and low power communications with sparse signaling codes
In bus communications methods and apparatus, a first set of physical signals representing the information to be conveyed over the bus is provided, and mapped to a codeword of a sparse signaling code, wherein a codeword is representable as a vector of a plurality of components, some of which are quiescent components and some of which are non-quiescent components, wherein the number of quiescent components and non-quiescent components meet a sparseness requirement.
1. A system comprising:
a communication bus with n independent signal paths for signal transmission, wherein n is an integer greater than or equal to 2;
a sparse encoder configured to generate a code word from a sparse signaling code, wherein the code word is from a set of code words that comprise vector components selected from a set of at least three values such that the resulting code word is balanced; and
a sparse driver configured to transmit the code word from the sparse signaling code on the communication bus by actively generating physical signals on the communications bus for each nonquiescent vector component, and passively obtaining physical signals for quiescent vector components on the communications bus.
2. The system of claim 1 wherein the physical signals representing quiescent vector components are obtained as a result of all components of the balanced sparse signaling code word summing to a constant value.
3. The system of claim 1 wherein the sparse signaling code comprises four nonquiescent components.
4. The system of claim 3 wherein the sparse signaling code comprises two nonquiescent components and three or more quiescent components.
5. The system of claim 1 , wherein the sparse driver comprises a plurality of controlled voltage sources, and each controlled voltage source is configured to provide an output proportional to the value of the vector component and a constant of proportionality α.
6. The system of claim 1 , wherein the sparse driver comprises a plurality of controlled current sources, and each controlled current source is configured to provide an output proportional to the value of the vector component and a constant of proportionality α.
7. The system of claim 1 , further comprising:
a signal-to-digital converter connected to the communication bus configured to generate a sampled representation of a received code word from a sparse signaling code, the signal-to-digital converter comprising:
a plurality of sample units configured to receive the code word and sample the vector elements of the code word, and form n samples corresponding to a permutation of a basis vector as generated by the sparse encoder; and,
a sorting unit configured to sort the n samples in ascending or descending order, and extract indices corresponding to a location and magnitude of nonquiescent portions of the code vector signaling code; and,
a sparse decoder configured to generate an output set of bits based on the indices provided by the plurality of sample units.
8. The system of claim 7 , wherein each of the plurality of sample units are selected form the group consisting of a sample-and-hold unit and a track-and-hold unit.
9. The system of claim 7 , wherein the sparse decoder comprises a look-up-table (LUT) to map the indices to the set of output bits.
10. A method comprising:
receiving, at a receiver input circuit, a first set of physical signals representing information, from a communication bus, wherein the first set comprises code words from a sparse signaling code in which code words comprise vector components selected from a set of at least three values;
determining, from the first set of physical signals, a second set of physical signals, wherein the second set of physical signals identifies nonquiescent components of the sparse signaling code received on the first set of physical signals,
determining from the second set of physical signals, the information transmitted on the communication bus,
wherein the sparse signaling code is a balanced code in that a measurable physical effect summed over nonquiescent vector components is equal to what the measurable physical effect summed would be if all of the vector components were quiescent.
11. The system of claim 10 wherein the sparse signaling code comprises four nonquiescent components.
12. The system of claim 10 wherein the sparse signaling code comprises two nonquiescent components and three or more quiescent component.
13. A method comprising:
receiving a plurality of bits representing information on a communications bus;
generating a code word from a sparse signaling code, wherein the code word is from a set of code words that comprise vector components selected from a set of at least three values such that the resulting code word is balanced; and
transmitting the code word from the sparse signaling code on the communication bus by actively generating physical signals on the communications bus for each nonquiescent vector component, and passively obtaining physical signals for quiescent vector components on the communications bus.
14. The system of claim 13 , wherein the sparse signaling code comprises code words that are permutations of a basis vector comprising elements selected from at least 3 values.
15. The system of claim 14 , wherein each code word comprises n elements, and n−2 elements are quiescent.
16. The system of claim 14 , wherein each code word contains two nonquiescent elements that have equal magnitude and opposite sign.