Rs-422/Rs-423 Compatibility; Terminal Connections - HP A4500A - VMEbus Single Board Computer 744 Motherboard Manual

8 A note on standards

RS-422/RS-423 compatibility

Terminal connections

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RS-422 and RS-423 are both compatible since they specify the same electrical
characteristics for the receiver. However, when connecting devices with different
baud rate and distance capabilities, the connection is limited to the baud rate and
distance supported by the device with the slower/shorter distance specification.
RS-423
Data
In
Data
Out
Direct terminal connections can be made using either the RS-232, RS-423, or RS-
422 standards. The table below gives details for each. The distance, data rate, and
distance/data rate ratio given here are all maximum values. The conductors column
gives the number of conductors necessary for a full-duplex direct connection.
Transmission
Single-ended
RS-232
RS-423 Single-ended
RS-422 Differential
Txa
Txb
Rxa
-
-
Rxb
+
Conductors Dist
3 50ft
4 4000ft
4 4000ft
RS-422
Rxa
-
Data
Out
Rxb
+
Txa
Data
In
Txb
Dist x Data
Data Rate
Rate
20 kBaud 100kBaud-ft
100 kBaud 4 MBaud-ft
10 MBaud 400 MBaud-ft