RS422,%20RS485,%20RS423,%20RS449%20and%20V.35 - PowerPoint PPT Presentation
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RS422,%20RS485,%20RS423,%20RS449%20and%20V.35
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RS422, RS485, RS423, RS449 and V.35 Introduction Serial interface standards that support longer cable lengths and higher data rate than RS232. – PowerPoint PPT presentation
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Title: RS422,%20RS485,%20RS423,%20RS449%20and%20V.35
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RS422, RS485, RS423, RS449 and V.35
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Introduction
- Serial interface standards that support longer
cable lengths and higher data rate than RS232.
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Agenda
- Balanced Line Interface
- RS422
- RS485
- RS423
- RS449
- V.35
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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)
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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
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Balanced Line Interface
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RS422
- Balanced line interface
- Mark VA VB gt 0.2V
- Space VA VB lt 0.2V
- Strictly for point-to-point communications
- Recommended maximum cable length is 4,000 ft. at
100kbps
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RS485
- RS422 with tri-state drivers
- Used in multi-drop networks
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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
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RS422, RS423 Speed and Length Limits
Source Beyda, Basic Data Communications,
Prentice Hall
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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
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V.35
- V.10 V.11
- Widely used to connect high speed (gt 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
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V.35 Connector
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V.35 Signals
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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
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Where to Get More Information
- www.sangoma.com/signal.htm
- www.arcelect.com/rs232.htm
