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Loopback Connectors
A
- 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).
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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.
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Table A-1 depicts the pin assignments for most loopback plugs and cables that may be used when testing a system.
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Table A-1
Signal Description |
EIA |
CCITT
# |
RS-449
"A" "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 |
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Table A-1 (Continued)
Signal Description |
EIA |
CCITT
# |
RS-449
"A" "B" | DIN 8
8-pin
round |
DB9
9-pin |
DB25
25-pin |
Direction |
Alpha
ID |
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 |
- Notes: 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. The wiring is shown in Figure A-1.
Figure A-1
25-pin RS-232 Port-to-Port Loopback Cable
- Use these wiring directions 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. The wiring is shown in Figure A-2.
Figure A-2
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 (see Figure A-3). Both connectors are male.
Figure A-3
- 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 (see Figure A-4).
Figure A-4
- 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 (see Figure A-5).
Figure A-5
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 (see Figure A-6):
Figure A-6
A.1 96-Pin Female Loopback Connector
- This 96-pin connector (see Figure A-7) can be ordered from Sun Microsystems (Part Number 370-1366).
Figure A-7
A.2 96-Pin Female Special Loopback Connector
- This 96-pin connector (see Figure A-8) can be ordered from Sun Microsystems (Part Number 370-1381).
Figure A-8
A.3 37-Pin RS-449 Loopback Cable
- Use these wiring instructions for a loopback cable for two 37-pin RS-449 synchronous ports (see Figure A-9).
Figure A-9
A.4 37-Pin RS-449 Loopback Plug
- Use these wiring instructions for making a male 37-pin RS-449 loopback plug (see Figure A-10). This connector is also available from Sun (Part Number 530- 1430).
Figure A-10
A.5 9-pin Male Single-port Loopback Plug
- Use these wiring directions for male 9-pin RS-232 and RS-423 single-port loopback plugs (see Figure A-11):
Figure A-11
A.6 9-pin Female Single-port Loopback Plug
- Use these wiring directions for female 9-pin RS-232 and RS-423 single-port loopback plugs (see Figure A-12):
Figure A-12
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Note - Use this loopback plug with the pcmciatest.
A.7 9-Pin to 25-Pin Port-to-Port Loopback Cable
- Use these wiring directions for a 9-pin RS-232 and RS-423 port to 25-pin RS-232 and RS 423 port loopback cables (see Figure A-13). Both connectors are male.
Figure A-13
A.8 9-Pin to 9-Pin Port-to-Port Loopback Cable
- Use these wiring directions for 9-pin RS-232 and RS 423 port to 9-pin RS-232 and RS-423 port loopback cables (see Figure A-14). Both connectors are male.
Figure A-14
- 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 pin1 to pin1, pin 2 to pin 2, and so on, for all pins. This loopback is a "straight-through" connection.
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