CN-0416

Circuit Note

Rev. 0 | Page 4 of 9

the receiver, whereas the inverting output of the driver is

shorted with the inverting input of the receiver. This

configuration allows for a 2-wire RS-485 network, but the bus

can only accommodate data transmission in one direction at a

time. The driver and receiver enable pins are required to assure

that only one driver is enabled to send data at a time. Figure 5

shows the connection setup for a three-slave node half-duplex

isolated RS-485 communication. Slave nodes are connected

through similar Ethernet jacks. For example, Slave A P5 is

connected to Slave B P5 using a straight-through CAT5 cable.

The master node is connected to a slave node via an opposite

Ethernet jack. For example, Slave A P5 is connected to P4 of the

master node using a straight-through CAT5 cable.

Figure 5. Three Node Half-Duplex Switch Settings and Connection Diagram Using ADM2682E Isolated RS-485 Communications

Table 3. Nodes and Switch Settings for Figure 5

Type of Node

Switch Settings

Master Node with Termination

S4 = half duplex, S5 = half duplex

S6 = terminated, S7 = terminated

Slave Node with Open Termination

S4 = half duplex, S5 = half duplex

S6 = open, S7 = open

End Slave Node with Termination

S4 = half duplex, S5 = half duplex

S6 = terminated, S7 = terminated

END SLAVE NODE

WITH TERMINATION

P24

S4 = HALF

S5 = HALF

S6 = TERM

S7 = TERM

GROUND A

P6

P4

P5

P11

SLAVE NODE

WITH OPEN TERMINATION

P24

S4 = HALF

S5 = HALF

S6 = OPEN

S7 = OPEN

GROUND A

STRAIGHT-THROUGH

CAT5 CABLE

STRAIGHT-THROUGH

CAT5 CABLE

STRAIGHT-THROUGH

CAT5 CABLE

P6

P4

P5

P11

SLAVE NODE

WITH OPEN TERMINATION

P24

S4 = HALF

S5 = HALF

S6 = OPEN

S7 = OPEN

GROUND A

P6

P4

P5

P11

MASTER NODE

WITH TERMINATION

MASTER

SERIAL

CONNECTION

P24

S4 = HALF

S5 = HALF

S6 = TERM

S7 = TERM

GROUND A

P6

P4

P5

P11