Rockwell Automation 2090 Ultra3000 Installation Manual - Manual (Page 95)

Publication 2098-IN003E-EN-P — April 2004
Ultra3000 Connector Data 2-53
Four-Wire RS-485 Connections
The Ultra3000 uses a variation of the RS-485 standard, known as
four-wire RS-485. Four-wire RS-485 uses one differential signal for
host to drive transmissions, and another differential signal for drive to
host transmissions. The RS-485 standard specifies a single differential
signal for transmissions in both directions.
The four-wire RS-485 configuration also allows the host to use a
RS-422 interface type. Because the host is driving multiple receivers
and receiving from multiple transmitters, RS-422 is limited to multiple
axes connections with 10 or less drives. The figure below summarizes
the four-wire RS-485, RS-422, and RS-485 standards.
Figure 2.58
RS-485/RS-422 Communication Comparison
Four-Wire RS-485
Differential
4 Wires
2 Signal Pairs
1 to 32 Transmitters
1 to 32 Receivers
RS-422
Differential
4 Wires
2 Signal Pairs
1 Transmitter
1 to 10 Receivers
RS-485 Standard
Differential
2 Wires
1 Signal Pair
1 to 32 Transmitters
1 to 32 Receivers
Note: Not applicable to Ultra3000
drives
1 2 32
1 2 10
1 2 32