The PassMark PM012 is a 9-pin female DE-9 serial loopback plug that connects directly to the male DE-9 port on a PC rear panel without any cabling. It allows diagnostic software — specifically PassMark BurnInTest Professional (Windows, v2.0 and later) and BurnInTest for Linux (v1.0 and later) — to verify the RS-232 UART by looping the port’s own transmit and handshake outputs back to its receive inputs. The governing electrical standard is ANSI/TIA-232-F (RS-232), and the 9-pin DE-9 connector form was standardised under TIA-574, introduced with the IBM PC/AT in 1984. The plug tests TxD/RxD data signals together with four RS-232 handshake lines: CTS, RTS, DSR, and DTR.
9 PIN D-SUB FEMALE Connector
| Name | Pin | Pin | Pin | Pin |
|---|---|---|---|---|
| Jumpering 1 | 2 | 3 | ||
| Jumpering 2 | 7 | 8 | ||
| Jumpering 3 | 1 | 4 | 6 |
Signals
- Jumpering 1 (pins 2–3) — loops RxD (pin 2, Receive Data) to TxD (pin 3, Transmit Data), enabling the UART to read back every byte it transmits.
- Jumpering 2 (pins 7–8) — loops RTS (pin 7, Request to Send) to CTS (pin 8, Clear to Send), verifying hardware flow-control handshaking.
- Jumpering 3 (pins 1–4–6) — ties DCD (pin 1, Data Carrier Detect), DTR (pin 4, Data Terminal Ready), and DSR (pin 6, Data Set Ready) together, completing the modem-ready signal group. Ring Indicator (pin 9) is not included in the PassMark wiring.
Notes
- The plug mates with the male DE-9 port (DTE connector) on the PC; no loopback cable is required.
- Pin 5 (Signal Ground) carries no loopback connection and should be left unconnected in the plug.
- PassMark offers only this 9-pin DE-9 serial loopback (PM012); their 25-pin plug (PM013) is a parallel-port loopback, not a serial one.
- Compatible software: BurnInTest Professional v2.0+ (Windows) and BurnInTest for Linux v1.0+.
References
- Serial (RS232) and Parallel Loopback Plugs Technical Specifications — PassMark Software
- Serial (RS232) and Parallel Loopback Plugs — PassMark Software
- Serial and Parallel Port External Loopback Wiring Diagrams — PC-Doctor, Inc.
- SunVTS 6.2 Test Reference Manual — Appendix A: Loopback Connectors — Oracle Corporation