Circuit to reduce rail noise voltage spikes due to switching on an input-output bus

A circuit to encode a word having a length, the circuit comprising:

• a stage to partition the word into smaller words each having a length less than the length of the word, each of the smaller words having a residue, the stage comprising a plurality of encoders, each encoder in the stage to encode a corresponding two of the smaller words into a corresponding larger word, each encoder to provide its corresponding larger word by concatenating a first of its corresponding smaller words with a first conditioning bit and the logical complement of a second of its corresponding smaller words provided the first and second residues of its first and second corresponding smaller words have the same algebraic signs and each are not zero, and by concatenating the first of its corresponding smaller words with a second conditioning bit and the second of its corresponding smaller words provided the first and second residues of its first and second corresponding smaller words have opposite algebraic signs and each are not zero, wherein the first conditioning bit is the logical complement of the second conditioning bit.

A circuit to encode a word w having a length n, the circuit comprising:

• a first stage to partition the word w into n/k words w(i), i=1, . . . , n/k each of length k where the concatenation w(1).w(2) . . . w(n/k) forms the word w, the first stage comprising n/2k encoders E(i), i=1, . . . , n/2k, wherein for each i=1, . . . , n/2k, encoder E(i) encodes the words w(2i) and w(2i−1) into a word w1(i) of length 2k+1 having an imbalance of k.

A circuit comprising:

• an encoder to encoder a word x having a residue and a word y having a residue into a word x.1. y provided the residues of the words x and y have the same algebraic sign, and into a word x.0. y provided the residues of the words x and y have opposite algebraic signs.

An apparatus comprising:

• L circuit stages stage(l), l=1, . . . , L, where L=log2 (n/k), wherein stage(1) partitions a word w having a length n into n/k words w0 (i), i=1, . . . , n/k each of length k;
• and
• for each l=1, 2, . . . , L, stage(l) comprises n/(2lk) circuit encoders El(i), i=1, . . . , n(2lk), where for each l=1, 2, . . . , L, for each i=1, . . . , n(2lk), El(i) encodes the words wl−1(2i) and wl−1(2i−1) into a word wl(i) of a length Length(i) having an imbalance of k, where for each i=2, . . . , L, Length(i) may be given by the recursion Length(p+1)=2Length(p)+1 for p=1, . . . , i−1 where Length(1)=2k+1.