This disclosure describes codes and techniques for magnetic recording. The coding schemes decrease bit error rates by decreasing total transitions in the encoded binary data compared to conventional codes. Additionally, instead of relying on a single coding scheme, an encoder and decoder are configured to switch between different coding schemes. By so doing, a variety of the coding schemes allows the encoded binary data to have a smaller bit error rate than a single coding scheme and have a maximum run-length less than or equal to a maximum run-length limitation of a magnetic disk.

A system includes a memory, a processor, an encoder, a head, and a decoder. The memory stores information. The processor processes information and controls operation of other components. The encoder encodes a first portion and a second portion of a servo track to form a first and second encoded values. The second code has a run length associated therewith. The first and second encoded values result in a Gray code. Each bit of the Gray code remains constant for at least a number of tracks corresponding to the run length. The head is configured to write the first and the second encoded values onto a media, and is configured to read the first and the second encoded values from the media. The decoder decodes the first encoded value and the second encoded value. The processor determines a servo track address from the decoded first value and the decoded second value.