RJ45 to serial DE-9

On Sep 6, 11:27, Curt Vendel wrote: well. the made That's somewhat Cisco-specific, if those are the standard colours. The standard colours for 8-way flat cable (in order in the cable) are 1 grey (some cables use white) 2 orange 3 black 4 red 5 green 6 yellow 7 blue 8 brown However, that's not always used in pre-made sockets. I have three different ones on the desk beside me. One goes blue, orange, black, red, green, yellow, brown, white, for example. That would give you the following pinout: RJ45 pin DE9 pin signal white 8 9 Ring Indicator brown 7 6 Data Set Ready yellow 6 2 Transmit Data green 5 5 Signal Ground red 4 5 Signal Ground black 3 3 Receive Data orange 2 4 Data Terminal Ready blue 1 7 Request To Send It would be much more usual to pair RTS with CTS (DE9 pin 8). One of the most common ways to wire an RJ45 for serial, are to wire the centre pair both to ground, with TxD on one side and RxD on the other. That way, if you turn the cable upside down you (as in a normal flat cable, one end is wired opposite to the other) you cross over RxD and TxD without losing the ground. TxD is pin 3 on a PC-compatible DE9 serial port, RxD is 2, and signal ground is pin 5, so that's fine. In a flat cable, the pairs start from the centre two wires, and work outwards to both sides, ending up with the 4th pair being the two outermost wires. But most systems that use this scheme put DTR and DSR (or occasionally DCD) on the next wires out from the centre (3rd pair), and DTR is on DE9 pin 4 (orange, OK) and DSR on pin 6 (brown, no I don't think so) and DCD on pin 1 (which Cisco obvioously doesn't use). The reason for putting DTR and DSR (or DCD) on the next two wires is again for the crossover effect. That's what DEC and several other companies do. Similarly, some systems put RTS and CTS on the outermost two wires. Looks like Cisco are using a non-standard colour order (or your RS adaptor is) but otherwise following one of the common wirings for flat cable (except for RI and RTS!). Of course, lots of people use UTP instead of flat cable. Then one way to start off is to put TxD and corresponding ground on pins 1+2 (which is one pair) and RxD and corresponding ground on the next pair (3+6). That way,a normal UTP crossover cable (one end wired to TIA 568A and the other to 568B) crosses things over correctly. That leaves 4+5 and 7+8 for other signals, usually unused but sometimes DTR+DSR and RTS+CTS (to keep each pair of signals in a single pair of wires, but it makes crossover cables "interesting"). DEC do it like that, they put 1 and 3 on the RJ45 to ground (actually Tx- and Rx-), TxD and RxD on 2 and 6, DTR and DSR on 7 and 8. Sun do a similar thing (but not quite the same). There is *no* standard for this, and I've found at least three common (and largely incompatible) wiring schemes, and several more obscure ones (Cabletron, Xylogics, ...) -- Pete Peter Turnbull Network Manager University of York