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RS422, RS485, RS423, RS449 and V.35

RS422, RS485, RS423, RS449 and V.35. Introduction . Serial interface standards that support longer cable lengths and higher data rate than RS232. Agenda. Balanced Line Interface RS422 RS485 RS423 RS449 V.35. Vocabulary. Skew Rate

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RS422, RS485, RS423, RS449 and V.35

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  1. RS422, RS485, RS423, RS449 and V.35 Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  2. Introduction • Serial interface standards that support longer cable lengths and higher data rate than RS232. Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  3. Agenda • Balanced Line Interface • RS422 • RS485 • RS423 • RS449 • V.35 Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  4. Vocabulary • Skew Rate • Measure the slope of signal transitions between Mark and Space • High skew rate causes interference to adjacent wires within the same cable (i.e. crosstalk) Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  5. Balanced (Differential) Line Interface • A pair of wires is used to carry each signal. The data is encoded and decoded as a differential voltage between the two lines • Advantages: • the interface is unaffected by differences in ground voltage between sender and receiver • if lines A and B are close together (e.g. in twisted pairs), they will be affected almost identically by external electromagnetic noise, which can then be eliminated at receiver Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  6. Balanced Line Interface Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  7. RS422 • Balanced line interface • Mark: VA – VB > +0.2V • Space: VA – VB < –0.2V • Strictly for point-to-point communications • Recommended maximum cable length is 4,000 ft. at 100kbps Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  8. RS485 • = RS422 with tri-state drivers • Used in multi-drop networks Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  9. RS423 • Single-ended (unbalanced) • one pair of wires per signal, one of it is GND • crosstalk is further reduced by using lower signal skew rate • Mark: –3.6 to –6V • Space: +3.6 to +6V • Can be used in one-to-many-points communications • Recommended maximum cable length is 40ft. at 100kbps, for 10 receivers Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  10. RS422, RS423 Speed and Length Limits Source: Beyda, Basic Data Communications, Prentice Hall Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  11. RS449 • Replace RS232 in high speed synchronous communication between DTE and DCE • Combine both balanced and unbalanced signals on the same interface • RS422: for fast changing signals like TD, RD and Clock • RS423: for slow changing signals like RTS, CTS, DSR, DTR, … etc. • Use a DB37 connector Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  12. V.35 • = V.10 + V.11 • Widely used to connect high speed (> 56kbps) DCEs in WAN (e.g. T1, Frame Relay, ATM networks) • Combine both balanced and unbalanced signals on the same interface • RS422: for fast changing signals like TD, RD and Clock • RS232: for slow changing signals like RTS, CTS, DSR, DTR, … etc. • Easily recognized by it bulky 34-pin connector Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  13. V.35 Connector Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  14. Pin Signal Pin Signal A Chassis Ground B Signal Ground C Request to Send D Clear to Send E Data Set Ready F Receive Line Signal Detect H Data Terminal Ready J Ring Indicator P Transmitted Data (Signal A) R Received Data (Signal A) S Transmitted Data (Signal B) T Received Data (Signal B) U Terminal Timing V Receive Timing A W Terminal Timing X Receive Timing Y Transmit Timing AA Transmit Timing V.35 Signals Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  15. Summary • RS422 and RS423 support longer cable length at higher data rates than RS232 • RS422: benefit from balanced line interface • RS423: benefit from individual ground return and lower skew rate • RS449 and V.35 combine both balanced and unbalanced signals on the same interface • RS449: RS422 + RS423 • V.35: RS422 + RS232 Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

  16. Where to Get More Information • www.sangoma.com/signal.htm • www.arcelect.com/rs232.htm Data Communications (E&T2760): RS422, RS485, RS423, RS449 and V.35

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