GE 90-30 PLC Series Installation And Hardware Manual page 385

The RS485 Port Isolator supports both port-to-port and multi-drop configurations (Figure E-4). For
installation information, refer to section 3 of the Serial Communications User's Manual
(GFK-0582). One configuration not covered in the User's Manual is the case where the Isolator is
powered by a source other than the host port. This configuration is used to prevent an interrupt in
communications if the host system requires a power cycle. It also prevents power loss to equipment
using the port for power. For this, you will need to build a custom cable as shown in Figure E-5.
Figure E-5. Multidrop Configuration Connecting Devices with 15-Pin Ports and 25-Pin Ports
GFK-0356Q Appendix E IC690ACC903 Port Isolator
Master PLC Master PLC
15
RT RT 9 9
15
pin
SD(B) SD(B) 13 13
pin
Fe
SD(A) SD(A) 12 12
Ma
ma
RD(B') RD(B') 11 11
le
Iso
le
RD(A') RD(A') 10 10
D-
D-
lat
co RTS(B) RTS(B) 14 14
co
nn
RTS(A) RTS(A) 6 6
nn
or
ect
CTS(B') CTS(B') 8 8
ect
or
CTS(A') CTS(A') 15 15
or
+5V +5V 5 5
GND GND 7 7
Terminate at first Terminate at first
and last drop only and last drop only
Make connectons Make connectons
Twisted Pairs Twisted Pairs
inside D connectors inside D connectors
To Other Slave Devices To Other Slave Devices
(Maximum of 8 devices on a multidrop) (Maximum of 8 devices on a multidrop)
E
Slave Device Slave Device
15 pin port 15 pin port
9 9 RT RT
11 11 RD(B') RD(B')
10 10 RD(A') RD(A')
13 13 SD(B) SD(B)
12 12 SD(A) SD(A)
8 8 CTS(B') CTS(B')
15 15 CTS(A') CTS(A')
14 14 RTS(B) RTS(B)
6 6 RTS(A) RTS(A)
1 1 SHLD SHLD
5 5 +5V +5V
7 7 GND GND
Slave Device Slave Device
15 pin port 15 pin port
9 9 RT RT
11 11 RD(B') RD(B')
10 10 RD(A') RD(A')
13 13 SD(B) SD(B)
12 12 SD(A) SD(A)
8 8 CTS(B') CTS(B')
15 15 CTS(A') CTS(A')
14 14 RTS(B) RTS(B)
6 6 RTS(A) RTS(A)
1 1 SHLD SHLD
5 5 +5V +5V
7 7 GND GND
Slave Device Slave Device
25 pin port 25 pin port
24 24 RT RT
25 25 RD(B') RD(B')
13 13 RD(A') RD(A')
21 21 SD(B) SD(B)
9 9 SD(A) SD(A)
23 23 CTS(B') CTS(B')
11 11 CTS(A') CTS(A')
22 22 RTS(B) RTS(B)
10 10 RTS(A) RTS(A)
7 7 GND GND
1 1 SHLD SHLD
E-5