Forward Latency
}Forward latency (FL) – block level
}Time between tokens consumed at inputs
and generated outputs
}Inputs tokens spread apart to avoid congestion slowing down results
}May be data-dependent
}(Forward) latency – system
}A sum of forward latencies through blocks
}Must account for causality of output tokens within blocks
}Earlier/latest arriving token may cause output token
}I.e., notion of critical path exists
module OR(L1, L2, R);
 `INPORT(L1,1);
 `INPORT(L2,1);
 `OUTPORT(R,1);
 `USES_CHANNEL
parameter FL = 2;
reg d1, d2;
always
begin
     fork
      `RECEIVE(L1,d1);
      `RECEIVE(L2,d2);
       join
       #FL;
      `SEND(R,d1 | d2);
  end
endmodule
CE-653 - Asynchronous Pipeline Performance
11/5/2014
4