Re: Getting a IIgs to play nice with a Mac

[Tristan Mumford <xtristan.xmumford@xgmail.xcom>]

David Empson wrote:

> Tristan Mumford <xtristan.xmumford@xgmail.xcom> wrote:
> 
>> David Empson wrote:
>> 
>> > <aiiadict@gmail.com> wrote:
>> > > Tristan Mumford <xtristan.xmumf...@xgmail.xcom> wrote:
>> > >> I'm using a couple of apple serial to serial adaptors. I'm doing it
>> > >> because I don't have an apple to apple cable. Would this be the
>> > >> problem?

-snip-

> It could be an adapter to convert from Mini-Din-8 to the original Mac
> serial port, which was a D9F. Its pinout has nothing in common with the
> PC standard serial port (D9M), and connecting the two of them directly
> together (or with a "standard" crossover cable) will at best achieve
> nothing and at worst could damage the serial ports (unlikely).

Ah. That I didn't know. So the original mac used a proprietary D9? 

> 
>> > AppleTalk with a "null modem" cable only requires the data lines and
>> > ground.
>> > 
>> > If you use a Mini-Din-8 to Serial adapter you are also clobbering half
>> > the balanced serial signal (the RX+ input is grounded and the TX+
>> > output is not connected) but it will probably work as long as you end
>> > up with the ground lines connected and Tx/Rx crossed over.
>> 
>> There is a chance it could work because of the way the signals are
>> converted but I'm less than sure.
> 
> LocalTalk may be fussier than standard serial, because it is running at
> a much higher speed than typical asynchronous data, and is using FM
> clocking within the data stream, effectively 460800 baud (230400 bps,
> but with one or two state transitions per bit - interleaved clock and
> data).

Now that I didn't know. I've been looking for exact info on the details of
how the data is sent etc. Looking in the wrong places though it seems.

> 
> It would be best to wire both RX+ and RX- through to TX+ and TX-, using
> a Mini-Din-8 at both ends and no adapters.
> 
> That means connecting the middle pin (4, ground) straight through,
> swapping over the outer pins of the middle row (3 & 5, TX- and RX-) and
> swapping over the outer pins of the third row (6 & 8, TX+ and RX+).
> Don't connect the other three pins, or if you must then swap 1 & 2, but
> let pin 7 go straight through (which will give you a full 8-way
> crossover cable).

-snip-

> The D9M adapter should be easy enough:
> 
> Mini-Din-8      D9M
> 1 HShkOut       7 RTS or 4 DTR, depending on desired function
> 2 HShkIn        8 CTS or 6 DSR, depending on desired function
> 3 TxD-          3 TxD
> 4 GND           5 GND
> 5 RxD-          2 RxD
> 6 TxD+          n.c.
> 7 GPI/DCD       1 DCD (probably)
> 8 RxD+          5 GND (to correctly bias the receiver)

That sounds pretty good.
It's definitely a case of building my own proper cable now.

It's not what could be called time critical, so I'll wait until I can get
the connectors to make a cable.

I also had a not so brilliant half-idea.
I've been looking for a way to get some kind of data connection from one end
of the house to the other. It really is a very long distance the cable has
to traverse. It occurred to me that because of the type of signal the Apple
cable would be more suitable. But then the mac can't talk to anything else,
so it's pointless. Unless it's possible to use its ports as an appletalk to
PPP bridge or something nightmarish like that.

Tristan.
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