50 pin SCSI to 50 pin centronics

From: Eric Chomko <chomko_at_greenbelt.com>
Date: Thu Apr 12 16:09:53 2001

Tony Duell wrote:

> > > IIRC, the RS232 standard specifies a 25 pin connector. So strictly there
> > > are no 9 pin RS232 ports. If you mean why do PC/AT machines have a DE9P
> > > for the serial port, it was because (a) 9 pins is enough for the active
> > > signals on said port and (b) you can fit a DE and a DB on a single PC
> > > bracket, so you could have a combined parallel/serial adapter card. Which
> > > IBM introduced with the PC/AT IIRC.
> >
> > Oh, but then you lose a lot of fun. The Amiga DB25 serial port features
> > among others audio output on some pins. =)
>
> So presumably using an all-pins-wired cable to link it to some true RS232
> device that happens to implement all the pins is a good way to let magic
> smoke out...
>
> I've actually seen a device that has a single DB25 with the stnadard set
> of RS232 signals on the stnadard pins (1-8 and 20 I think), and a
> TTL-level Centronics-like parallel port on the other pins. Now that is a
> device that you certainly don't connect to just any RS232 port.

Same goes with SCSI. I heard a story where a Mac was connected to a RS-232
terminal
via the Mac's SCSI connector. Ouch! The motherboard stopped functioning after
some of the terminal's +/- 12 volts started flowing thru it.
Received on Thu Apr 12 2001 - 16:09:53 BST