RAD Data Communications equipped devices such as the FPS-8 frame-relay switch with a DB-25 console port. Because most personal computers from the late 1990s onward carry only a DE-9 (9-pin) serial port, a crossed adapter cable is required to connect a PC COM port to the device’s 25-pin management connector. The cable crosses the standard EIA-232 (TIA/EIA-232-F) signals — TxD, RxD, DTR, DSR, DCD, RTS, CTS, and GND — between the two D-sub connectors. RAD did not publish a public pinout specification for this cable; the wiring table below reflects the signals labelled on the connector ends.
9 pin D-SUB female connector to the computer
9 pin D-SUB female connector to the device
| PC Pin name | PC Pin | Direction | RAD switch Pin | RAD switch Pin name | Description |
|---|---|---|---|---|---|
| DCD | 1 | IN | 2 | May be skipped if shorted with DSR in DB-9 connector | |
| RxD | 2 | IN | 5 | ||
| TxD | 3 | OUT | 6 | ||
| DTR | 4 | OUT | 3 | ||
| GND | 5 | - | 4 | ||
| DSR | 6 | IN | 1 | May be shorted with DCD | |
| RTS | 7 | OUT | 8 | ||
| CTS | 8 | IN | 7 | ||
| RI | 9 | Not used |
Notes
The DE-9 end connects to the PC COM port (DTE). Pin 1 (DCD) may be looped to Pin 6 (DSR) inside the DE-9 shell if the terminal emulator requires both signals asserted; Pin 9 (RI) is unused. The RAD switch end is a 25-pin D-sub; the RAD switch pin-name column is not publicly documented. EIA-232 specifies a maximum cable capacitance of 2500 pF and a typical usable length of approximately 15 m at standard baud rates up to 20 kbps.
Signals
- DCD — Data Carrier Detect; input to PC; may be shorted to DSR
- RxD — Receive Data; data from device to PC
- TxD — Transmit Data; data from PC to device
- DTR — Data Terminal Ready; output from PC
- GND — Signal ground
- DSR — Data Set Ready; input to PC; may be shorted to DCD
- RTS — Request To Send; output from PC
- CTS — Clear To Send; input to PC
- RI — Ring Indicator; not used on this cable
References
- Interface Circuits for TIA/EIA-232-F (SLLA037A) — Texas Instruments, September 2002