Coding system and method for partial response channels

1. Field of the Invention A system and method for reading data to and writing data from multi-level (M-ary) partial response channels uses a trellis coder to encode an input bit stream sequence into a stream of multi-level data symbols. The data symbols are written to the partial response channel using any of a number of techniques. Preferably, the trellis coder anticipates the modulation transfer function of the partial response channel in encoding the data. Because the partial response channel has its own transfer function, the relationship between the data read from the channel and the actual input data bits is a function not only of the data encoder but also of the partial response channel. Therefore, a decoder specification used to implement the decoder takes into account the effect of the trellis encoder as well as the effect of the partial response channel.