2-19
2
Figure 2-9 shows a two wire RS-485 network connection. The dotted lines
show the bias pin connections. If the 2307 is to be used in a 2-wire, RS-485
half-duplex network, the like polarity RD and SD lines would be connected
together and the RS485 mode would need to be enabled. The bias voltage
pins on the 2307's serial connector have 2.2 Kohm on board resistors and
can be used to bias the signal lines without having to use external resistors.
SD(B)
SD(A)
RD(A)
RD(B)
0V Bias
+V Bias
2307
RS-485
Network
1
2
3
4
5
6
7
8
9
Note: Rev X1 PC Board Assemblies do not have a 0V Bias Connection.
Figure 2-9 2307 RS-485 Connections
TABLE 2-3 2307 J3 PIN ASSIGNMENTS
RS-232
—
BA
BB
—
AB
—
—
—
—
Pin
1
2
3
4
5
6
7
8
9
Direction
In Out
→
→
←
←
←
Signal
Send Data (A)
Send Data (B)
Receive Data (B)
Receive Data (A)
Ground
2.2 Kohm to GND
2.2 Kohm to +5 V
RS-422
RS-485
SD(B)
SD(A)
RD(A)
RS(B)
GND
—
0V Bias
+V Bias
—
Note: 0V Bias output and its internal resistor not available on Rev X1 PCBs.
Use an external 2.2 Kohm resistor to pin 5 to pull down the SD(A) signal.
