B&B Electronics 3PCIOU4 - Manual - Manual (Page 43)

RS-422/ 485 Connections/Operation
Document Number 3PCI-0712m Chapter 8 37
485, using the A connection for ―+‖ and the B for ―-―. In such cases, reversing the line
pair permits operation.
4-Wire RS-422 and RS-485 Connections
RS-422 Point to Point Connection
For RS-422 point to point communications connect the MIport card and to one RS-422
device only.
1. Connect the TD(B) pin #2 on the computer to RD(B) on the device.
2. Connect the TD(A) pin #3 on the computer to RD(A) on the device.
3. Connect the RD(B) pin #9 on the computer to TD(B) on the device.
4. Connect the RD(A) pin #1 on the computer to TD(A) on the device.
5. Connect the Signal Ground pin #5 to Signal Ground on the device.
RS-422 Point to Multipoint Connection
In a multi-slave RS-422 connection, TD(B) and TD(A) connect to RD(B) and RD(A) on
all the slaves. If the slaves have Transmit connections, only one device can be
connected back to the master.
Figure 21. RS-422 Master to RS-422 Receive Only Devices