GFK-0356Q Appendix E IC690ACC903 Port Isolator E-5
E
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.
Master PLC
To Other Slave Devices
(Maximum of 8 devices on a multidrop)
Slave Device
15 pin port
Slave Device
15 pin port
Terminate at first
and last drop only
9
13
12
11
10
14
6
8
15
5
7
RT
SD(B)
SD(A)
RD(B')
RD(A')
RTS(B)
RTS(A)
CTS(B')
CTS(A')
+5V
GND
9
11
10
13
12
8
15
14
6
1
5
7
RT
RD(B')
RD(A')
SD(B)
SD(A)
CTS(B')
CTS(A')
RTS(B)
RTS(A)
SHLD
+5V
GND
9
11
10
13
12
8
15
14
6
1
5
7
RT
RD(B')
RD(A')
SD(B)
SD(A)
CTS(B')
CTS(A')
RTS(B)
RTS(A)
SHLD
+5V
GND
24
25
13
21
9
23
11
22
10
7
1
RT
RD(B')
RD(A')
SD(B)
SD(A)
CTS(B')
CTS(A')
RTS(B)
RTS(A)
GND
SHLD
Slave Device
25 pin port
Twisted Pairs
Make connectons
inside D connectors
Iso
lat
or
15
pin
Fe
ma
le
D-
co
nn
ect
or
15
pin
Ma
le
D-
co
nn
ect
or
Master PLC
To Other Slave Devices
(Maximum of 8 devices on a multidrop)
Slave Device
15 pin port
Slave Device
15 pin port
Terminate at first
and last drop only
9
13
12
11
10
14
6
8
15
5
7
RT
SD(B)
SD(A)
RD(B')
RD(A')
RTS(B)
RTS(A)
CTS(B')
CTS(A')
+5V
GND
9
11
10
13
12
8
15
14
6
1
5
7
RT
RD(B')
RD(A')
SD(B)
SD(A)
CTS(B')
CTS(A')
RTS(B)
RTS(A)
SHLD
+5V
GND
9
11
10
13
12
8
15
14
6
1
5
7
RT
RD(B')
RD(A')
SD(B)
SD(A)
CTS(B')
CTS(A')
RTS(B)
RTS(A)
SHLD
+5V
GND
24
25
13
21
9
23
11
22
10
7
1
RT
RD(B')
RD(A')
SD(B)
SD(A)
CTS(B')
CTS(A')
RTS(B)
RTS(A)
GND
SHLD
Slave Device
25 pin port
Twisted Pairs
Make connectons
inside D connectors
Isolator
15 pin Female D-connector
15 pin Male D-connector
Figure E-5. Multidrop Configuration Connecting Devices with 15-Pin Ports and 25-Pin Ports
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