Appendix A Loopback Connectors
Loopback connectors are designed for the testing of communication ports. They take the form of either a single plug or a port-to-port cable with some communication connections shorted (looped-back).
Note -
Loopback connectors must be wired properly and connected firmly for the Serial Port tests to work correctly. Miswired, poorly soldered, or missing loopback connectors can cause erroneous diagnostic error messages.
Table A-1 depicts the pin assignments for most loopback plugs and cables that may be used when testing a system.
Table A-1 Loopback Connector Pin Assignments|
Signal Description |
EIA |
CCITT # |
RS-449 "A" |
RS-449 "B" |
DIN 8 8-pin round |
DB9 9-pin |
DB25 25-pin |
Direction |
Alpha ID |
|---|---|---|---|---|---|---|---|---|---|
|
Chassis/Frame Ground |
AA |
101 |
1 |
NC* |
NC* |
NC* |
1 |
None |
AA |
|
Transmit Data (TxDa) |
BA |
103 |
4 |
22 |
3 |
3 |
2 |
Output |
BA |
|
Receive Data (RxDa) |
BB |
104 |
6 |
24 |
5 |
2 |
3 |
Input |
BB |
|
Request To Send (RTSa) |
CA |
105 |
7 |
25 |
6 |
7 |
4 |
Output |
CA |
|
Clear To Send (CTSa) |
CB |
106 |
9 |
27 |
2 |
8 |
5 |
Input |
CB |
|
Data Set Ready (DSRa) |
CC |
107 |
11 |
29 |
NC* |
6 |
6 |
Input/ output |
CC |
|
Signal Ground (SG) |
AB |
102 |
19 |
NC* |
4 |
5 |
7 |
None |
AB |
|
Data Carrier Detect (DCDa) |
CF |
109 |
13 |
31 |
7 |
1 |
8 |
Input |
CF |
|
Transmit Clock In (TRxCa) |
DB |
114 |
5 |
23 |
NC* |
NC* |
15 |
Input |
DB |
|
Receive Clock In (RTxCa) |
DD |
115 |
8 |
26 |
8 |
NC* |
17 |
Input |
DD |
|
Data Terminal Ready (DTRa) |
CD |
108 |
12 |
30 |
1 |
4 |
20 |
Output |
CD |
|
External Clock Out (TRxCa) |
DA |
113 |
17 |
35 |
NC* |
NC* |
24 |
Output |
DA |
|
Secondary Data Carrier Detect (DCDb) |
SCF |
122 |
NC* |
NC* |
NC* |
NC* |
12 |
Input |
SCF |
|
Secondary Clear to Send (CTSb) |
SCB |
121 |
NC* |
NC* |
NC* |
NC* |
13 |
Input |
SCB |
|
Secondary Transmit Data (TxDb) |
SBA |
118 |
NC* |
NC* |
NC* |
NC* |
14 |
Output |
SBA |
|
Secondary Receive Data (RxDb) |
SBB |
119 |
NC* |
NC* |
NC* |
NC* |
16 |
Input |
SBB |
|
Secondary Request to Send (RTSb) |
SCA |
120 |
NC* |
NC* |
NC* |
NC* |
19 |
Output |
SCA |
*NC = No connection
25-Pin RS-232 Loopback Plug
The RS-232 and RS-423 single-port loopback plug is a specially wired male DB-25 connector. It is plugged in to a serial port in the back of the system under test.
Figure A-1 25-pin RS-232 Loopback Plug Wiring Diagram
25-pin RS-232 Port-to-Port Loopback Cable
Use these wiring instructions for 25-pin RS-232 and RS-423 port to 25-pin RS 232 and RS 423 port loopback cables (two DB-25 connections). It is plugged into a pair of serial ports in the back of the system under test. Both connectors are male.
Figure A-2 25-pin RS-232 Port-to-Port Loopback Cable Wiring Diagram
8-Pin to 8-Pin Loopback Cable
Use these wiring directions for 8-pin round DIN RS-232 port to RS-423 to 8-pin round-DIN RS-232 and RS-423 port loopback cable. Both connectors are male.
Figure A-3 8-Pin to 8-Pin Loopback Cable Wiring Diagram
Pin 8, Receive clock In (DD), remains unconnected.
8-Pin Loopback Plug
Use these wiring directions for male 8-pin round-DIN RS-232 and RS-423 single-port loopback plugs.
Figure A-4 8-Pin Loopback Plug Wiring Diagram
Pin 8, Receive Clock In (DD), remains unconnected.
25-pin Port A-to-Port B Loopback Plug
Use these wiring directions for a 25-pin Port A to Port B loopback plug for most systems.
Figure A-5 Port A-to-Port B Loopback Plug Wiring Diagram
25-pin Port A-to-A Port B-to-B Loopback Plug
If your system has a single communication port to connect it to peripherals, use these wiring instructions for making a male 25-pin loopback plug for that communication port.
Figure A-6 Port A-to-A, Port B-to-B Loopback Plug Wiring Diagram
96-Pin Female Loopback Connector
This 96-pin connector can be ordered from Sun (part number 370-1366).
Figure A-7 96-Pin Female Loopback Connector Wiring Diagram
96-Pin Female Special Loopback Connector
This 96-pin connector can be ordered from Sun (part number 370-1381).
Figure A-8 96-Pin Female Special Loopback Connector Wiring Diagram
37-Pin RS-449 Loopback Cable
Use these wiring instructions for a loopback cable for two 37-pin RS-449 synchronous ports.
Figure A-9 37-Pin RS-449 Loopback Cable Wiring Diagram
37-Pin RS-449 Loopback Plug
Use these wiring instructions for making a male 37-pin RS-449 loopback plug. This connector is also available from Sun (part number 530-1430).
Figure A-10 37-Pin RS-449 Loopback Plug Wiring Diagram
9-pin Male Single-Port Loopback Plug
Use these wiring instructions for male 9-pin RS-232 and RS-423 single-port loopback plugs.
Figure A-11 9-Pin Male Single-Port Loopback Plug Wiring Diagram
9-pin Female Single-Port Loopback Plug
Use these wiring directions for female 9-pin RS-232 and RS-423 single-port loopback plugs. Use this loopback plug with the pcmciatest.
Figure A-12 9-Pin Female Single-Port Loopback Plug Wiring Diagram
9-Pin to 25-Pin Port-to-Port Loopback Cable
Use these wiring instructions for a 9-pin RS-232 and RS-423 port to 25-pin RS-232 and RS 423 port loopback cables. Both connectors are male.
Figure A-13 9-Pin to 25-Pin Port-to-Port Loopback Cable Wiring Diagram
9-Pin to 9-Pin Port-to-Port Loopback Cable
Use these wiring instructions for 9-pin RS-232 and RS 423 port to 9-pin RS-232 and RS-423 port loopback cables. Both connectors are male.
Figure A-14 9-Pin to 9-Pin Port-to-Port Loopback Cable Wiring Diagram
Please note that this cable has no Sun part number assigned to it.
NT to TE Loopback Cable
Using two standard RJ45 connectors, and connect pin 1 to pin 1, pin 2 to pin 2, and so on, for all pins. This loopback is a "straight-through" connection.
Twisted-Pair Ethernet (TPE) Loopback Cable
Use these wiring instructions for standard RJ-45 connectors. This loopback cable is used in netlbtest for eri devices.
Figure A-15 Twisted-Pair Ethernet (TPE) Loopback Cable Wiring Diagram
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