Augmented Parity Check Codes for Encoding of Asynchronous Sequential Machines

Critical races can be avoided in the binary encoding of asynchronous sequential machines by making use of general codes employing-multistep changes in secondary variables to accomplish transitions between states. The shortest length code of this type presently available is Huffman's internmeshed row set code, which encodes race-free any 2
^S
O-row flow table with 2S
o
-1 bits. In this paper, a new class of codes called augmented parity check codes (APC codes) is introduced and proposed for race-free encoding. Some of the properties of these codes suggest that minimum codes may require only on the order of S
o
+ log
2
S
O
bits.