12 Apr
2001
12 Apr
'01
5:09 p.m.
Tony Duell wrote:
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.
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. =)