Actually, it is quite normal for a UPS to have both inputs and outputs.
There is no point in leaving the UPS on battery after the computer has
shutdown, so the computer can issue a signal that will cause the UPS to
switch off. That way, if you have repeated outages in a short period of
time, you will still have battery capacity to deal with them.

I'll have to check this work out later. When I retire my old APC, I may
put on my Quadra.

Seth Henry
jshenry@net-noise.com

On Thu, 25 Jan 2001, Bill Studenmund wrote:

> On Wed, 24 Jan 2001, Segfault wrote:
>
> > Hi all,
> >
> > I'm trying to make a UPS package I found for FreeBSD (which I used to use
> > on a PC) to work on my Mac Quadra 605.
> >
> > What the program does is monitor and alter the signal level of specific
> > pins of a serial port connected to the UPS.
> >
> > >From the source, the various ports monitored or changed are RTS, DTR, RNG
> > and other pins (TIOCM_RTS, TIOCM_DTR and TIOCM_RNG respectively).
> > However, I don't know which pins are mapped to which. PCs have pins
> > labeled as RTS, CTS, DSR, DCD, TxD and RxD but Macs have round serial
> > port connectors with pins labeled as HSKo, HSKi, TxD-, RxD-, TxD+, GPi
> > and RxD+ instead.
>
> I'm a little confused. I'd expect the UPS to be telling you what is going
> on, but RTS and DTR are outputs - i.e. if we're talking about the Mac,
> they are outputs from the mac to the UPS. Which seems backwards.
>
> Pin mapping will really depend on the cable you're using, so I'll just go
> over which pins NetBSD worries about, and let you deal with your
> cable. :-)
>
> HSKo == DTR
> HSKi == CTS
> GPi  == DCD
> TxD+ == unused		Note that TxD+/- form a differential pair
> TxD- == TD		which helps get better signals strength
> RxD+ == connect this to ground
> RxD- == RD		RxD+/- are also a differential pair
>
> > Therefore, I would like to know which pins are mapped to which. For
> > example, if I checked the signal level of the pin "RTS", which pin on my
> > Mac would actually be checked?
>
> Note: RTS isn't an output on Mac Serial ports.
>
> Here's where I'm confused. Your software should be DRIVING the levels of
> output pins, not checking them. :-) I'd expect that you'd really look at
> are the inputs.
>
> Take care,
>
> Bill
>
>