Partial response channel having combined MTR and parity constraints

A method of encoding successive data words into successive code words for transmission through a channel, the method comprising steps of:

• (a) mapping each successive data word into a corresponding one of the code words according to a selected code;
• and
• (b) concatenating the successive code words to form an encoded bit stream having a plurality of even and odd indexed bit positions, wherein the mapping step (a) enforces a parity constraint on the selected code and a maximum transition run constraint on the selected code such that the encoded bit stream has a maximum possible run of one consecutive transition beginning in either one of the even or odd indexed bit positions in the encoded bit stream and has a maximum possible run of two consecutive transitions beginning in the other of the even or odd indexed bit positions in the encoded bit stream.

A data storage read channel for use in detecting successive code words in a storage channel output, the successive code words being encoded according to a code, the read channel comprising:

• a likelihood sequence detector, which detects the successive code words, wherein the detector has a detection sequence that effectively disallows detection of bit sequences in the storage channel output having greater than one consecutive transition beginning at either odd or even indexed bit positions in the bit sequence, bit sequences in the channel output having greater than two consecutive transitions beginning at the other of the odd or even indexed bit positions, and bit sequences in the channel output having a disallowed parity.