mac serial pinouts

From: Lawrence Walker <lgwalker_at_look.ca>
Date: Mon Oct 9 15:31:42 2000

> > > > Can anyone tell me which pins (and I don't know the numbering
> > > > scheme, so please include that) are transmit, receive, and gnd
> > > > on a Mac 8-pin mini-din port?
> > >
> > > The pinout I have numbers the pins like this :
> > >
> > > o o o
> > > 8 7 6
> > > o o o
> > > 5 4 3
> > > o o
> > > 2 1
> > >
> > > Looking into the socket.
> > >
> > > The pinout is :
> > > 1 Handshake output
> > > 2 Handshake (or external clock) input
> > > 3 Tx Data -
> > > 4 Ground
> > > 5 Rx Data -
> > > 6 Tx Data +
> > > 7 No Connection
> > > 8 Rx Data +
>
> [...]
>
> > A problem exists with Mac cables. Unless you're using the newer
> > hispeed cable you can't connect to your ISP even tho it seems to
> > test ok with a terminal program. I ran across this problem in trying
> >
>
> It appaers that a hispeed cable is one that links pin 7 on the Mac to
> CD (pin 8 o na DB25 RS232 connector), right?
>
> > to hook my Mac up. I fussed and fumed over it for about a month
> > before stumbling across the solution.
> > There is nothing to physically indicate any differences between the
> > 2 cables. A little.Practical Peripherals file explains it as follows:
> >
> > The Macintosh has too few pins for a full RS-232 implementation.
> > The RS-23 standard has 25 pins, however, most Mac ports have
> > only 8 pins. The following pins are needed when talking to a high-
>
> However, very few systems use more than 8 or 9 of those pins (the PC 9
> pin serial port works simply because 9 signals is enough for
> asynchronous links).
>
> On the other hand, the Mac cuts down the number of signals available
> because it uses RS422 differential signals for TxD and RxD (so 2 pins
> for each of these).
>
> [...]
>
> > Here's the pin outs for that cable:
> >
> > Function (Mac) Function (RS-232) Pin (Mac) Pin (RS-232)
> > Receive data Receive data 5 3
> > Send data Send data 3 2
> > Ground Ground 4 & 8 7
> > HSKi CTS 2 5
> > HSKo RTS & DTR 1 4 &20
> > GPi CD 7 8
> >
> > Unfortunately, not all Macs support Pin 7 (GPi) thus leaving us with
> > keeping CD on at all times. Also, since DTR is tied to RTS a high-
>
> Yes, and that is a problem. The Mac+ (which is the machine I have
> documentation on) has no connection to pin 7 on either of its serial
> ports. I've pulled a machine apart to check and that pin goes nowhere.
>
> So if you use a hispeed cable on a Mac+ and possibly other older Macs
> (this is classiccmp, after all, where people use older machines) then
> you'll have the same problem as if you didn't wire up CD at all. The
> CD signal will go nowhere.
>
> If you can manage without CD (or any other signal going in on pin 7 of
> the Mac serial port) then it's a good idea to do so IMHO.
>
> -tony
>
 The whole port thing on the Mac is a real can of worms. On
reading your post I went scurrying to my puter specs and tips
directory and computer books and my head is still spinning.
 Aside from the variance of connectors; the m.128-512 with
DB(DE?)9, the Mac+ - Mac ll(?) with 8pin mini-DINs and the later
models with 9pin mini-DINs not to mention the ethernet AUUI 15
or the abortive HDI-45 monitor port and the cabling problem, you
have to contend with Apples nominclature. I have various Macs
including a 512,+, SE, IIci,and LCIII, as well as various Apple
printers. Labeling the cables would seem to be my best solution.

The 9pin miniDIN adds a +5 v source on pin9 but the sockets are
backward compatible. The hi-speed cable I use is an 8pin miniDIN.

  My PowerMac gives these specs:
 
     Pin Name Function
     --- ---- --------
    1 SCLK(out) Reset pod or get pod attention
     2 Sync(in)/SCLK(in) Serial clock from pod
     3 TxD- Transmit -
     4 Gnd/shield Ground
     5 RxD- Receive -
     6 TxD+ Transmit +
     7 Wakeup/TxHS Wake up CPU or do DMA handshake
     8 RxD+ Receive +
     9 +5 V Power to pod (350 mA maximum)

So it uses the previously not-used pin 7 with no reference to Carrier
Detect, unless that's what they mean with "wake up CPU".
 And (of course !) Apple uses new names for it's ports since HSK
didn't catch on. I guess a "pod" is a serial device not something
that grows on vines or a space capsule. :^)

 I've got about a dozen or so Mac books except the reputedly "best"
Larry Pina one, and none of them mention this problem.
 I've also got a NEXT which IIRC uses RS423 prot. but has a
similiar miniDIN. These guys really keep the cable manufacturers
busy. Again the specs are hard to find. Is there such a thing as a
repositry of cable connection specs ?

ciao larry





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Received on Mon Oct 09 2000 - 15:31:42 BST