3.5. Viterbi IP Core Interfaces and Signals
    The Viterbi Avalon-ST interface supports backpressure, which is a flow control mechanism, where a sink can indicate to a source to stop sending data. 
  
 
  The ready latency on the Avalon-ST input interface is 1.
You may achieve a higher clock rate by driving the source ready signal source_rdy of the Viterbi high, and not connecting the sink ready signal sink_rdy.