propagation time


critical length of a bus line occurring at the point where the return propagation delay (tprop(total)) of a signal through a line, equals the transition time(tt) of a signal (the greater between rise and fall times)


  • NOTE Network Critical Length = tt = tprop(total)
  • NOTE typical ISO or RS-485 driver has a 50 ns transition time, and when considering a typical twisted-pair transmission line prop delay of 5 ns/m, the return delay for one meter becomes 10ns/m. The critical length becomes 5 m (50 ns / 10ns/m = 5 m), and the max un-terminated stub length for the network is 1/3rd of the critical length, or 5/3 m (1,67 m). [CANopen - CiA Standard 301 V4.2.0]
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