A Viterbi detector for a PR4,ML data channel includes a data sample input for receiving digital data samples from a source. Digital data samples are taken of data which has been coded in a predetermined data code format and which has been passed through a data degrading channel. A delay circuit delays the digital data samples received at the data sample input. A delay selector controls an output of the delay circuit in accordance with a feedback control bit value. An adder circuit combines data samples from the data sample input with delayed samples from the delay circuit to produce a sum. A threshold input receives programmable positive and negative data threshold values. A threshold selector puts out either the positive or the negative threshold values in accordance with a sign bit control value. A comparator compares the sum with a selected threshold value and puts out a logical value based upon comparison thereof. It includes Viterbi decision state logic for determining the sign bit control value, the feedback control bit value, and two raw data bits for each incoming data sample. A memory path circuit decodes a sequence of consecutive values of the raw data bits in accordance with a predetermined maximum likelihood trellis decode logic table related to the predetermined data code format and puts out a sequence of detected code bits.