Serial, RS485: Difference between revisions
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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). | 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). | ||
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<TABLE Width="350"> | |||
Here is an image showing balanced differential communications where noise that is induced is canceled out be the opposite pair | <TR><TD>Here is an image showing balanced differential communications where noise that is induced is canceled out be the opposite pair</TD><TD>[[Image:Twisted_immunity.png]]</TD></TR> | ||
[[Image:Twisted_immunity.png]] | </TABLE> | ||
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==Advantages & Disadvantages== | ==Advantages & Disadvantages== | ||
Revision as of 21:18, 17 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).
| Here is an image showing balanced differential communications where noise that is induced is canceled out be the opposite pair |  |
Advantages & Disadvantages
Advantages of RS-422 and RS-485:
- Higher data rates up to 10Mbps
- 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
- More cabling required compared to RS-232
- Not as common compared to RS-232