M of n codes

An "m" of "n" code is a separable error detection code with a code word length of "n" bits, where each code word contains exactly "m" instances of a "one." A single bit error will cause the code word to have either "m" + 1 or "m" – 1 "ones." An example "m"-of-"n" code is the 2 of 5 code used by the U.S. Post Office.

The simplest implementation is to append a string of ones to the original data until it contains "m" ones, then append zeros to create a code of length "n".

Example: