User's Guide _______________________________________________________________________
54 _______________________________________________________________________________
6.
If you use RS-485 (or RS-422) to connect just one transmitter to
a master computer, enable the internal termination of transmitter
by switching switches 1 and 2 ON. Make sure that the master's
end of the line is also terminated (by using master's internal
termination or with a separate terminator).
If you are connecting many transmitters to the same RS-485 bus,
make sure that switches 1 and 2 are OFF and terminate the bus
with separate terminators at both ends. This allows removing
any transmitter without blocking the bus operation.
NOTE
If you use the internal termination of the transmitter at the end of the
RS-485 bus (instead of using separate terminators) removing that
transmitter will block the bus operation.
7.
Use the bus type (4-wire/2-wire) to select the selection switch 3.
In 4-wire mode RS-485 master sends data to the transmitter
through terminals RxA and RxB and receives data from
transmitter through terminals TxA and TxB.
Figure 34
4-Wire RS-485 Bus
Table 5
4-Wire (Switch 3: On)
RS-485 master
Data
TRANSMITTER
TxA
→
RxA
TxB
→
RxB
RxA
←
TxA
RxB
←
TxB
