Serial, RS485: Difference between revisions
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Advantages of RS-422 and RS-485: | Advantages of RS-422 and RS-485: | ||
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<LI>Higher data rates up to | <LI>Higher data rates up to 35Mbps | ||
<LI>Longer cable lengths up to 4000 Feet | <LI>Longer cable lengths up to 4000 Feet | ||
<LI>Noise rejection or total noise immunity | <LI>Noise rejection or total noise immunity | ||
Revision as of 02:08, 18 March 2009
Overview
RS-485 is very similar to RS-422 where it is balanced pair communications in order to archive high bit rates over long distances with minimal or no noise introduced into the data.
EIA-485 only specifies electrical characteristics of the driver and the receiver. It does not specify or recommend any data protocol. EIA-485 enables the configuration of inexpensive local networks and multidrop communications links. It offers high data transmission speeds (35 Mbit/s up to 10 m and 100 kbit/s at 1200 m). Since it uses a differential balanced line over twisted pair (like EIA-422), it can span relatively large distances (up to 4000 feet or just over 1200 metres).
| In this image we are showing balanced differential communications where noise that is induced is canceled out by each other by the opposing pair basically being at 180 degrees out of phase in relation of each other at all times, thus allowing to achieve very high baud rates over greater distances. |  |
Advantages & Disadvantages
Advantages of RS-422 and RS-485:
- Higher data rates up to 35Mbps
- Longer cable lengths up to 4000 Feet
- Noise rejection or total noise immunity
- Any ground loops would not affect data transmission
Disadvantages of RS-422 and RS-485:
- Only one transmitter for most applications (applies only to RS-422)
- More cabling required compared to RS-232
- Not as common compared to RS-232