SLLA272D February   2008  – May 2021

 

  1.   Trademarks
  2. 1 Introduction
  3. 2 Standard and Features
  4. 3 Network Topology
  5. 4 Signal Levels
  6. 5 Cable Type
  7. 6 Bus Termination and Stub Length
  8. 7 Failsafe
  9. 8 Bus Loading
  10. 9 Data Rate Versus Bus Length
  11. 10Minimum Node Spacing
  12. 11Grounding and Isolation
  13. 12Conclusion
    1. 12.1 References
  14. 13Revision History

4 Signal Levels

RS-485 standard conform drivers provide a differential output of a minimum 1.5 V across a 54-Ω load, whereas standard conform receivers detect a differential input down to 200 mV. The two values provide sufficient margin for a reliable data transmission even under severe signal degradation across the cable and connectors. This robustness is the main reason why RS-485 is well suited for long-distance networking in noisy environment.

GUID-B63E78A2-8611-4260-897B-DD89F8DDDFED-low.gif Figure 4-1 RS-485 Specified Minimum Bus Signal Levels