mac serial pinouts

From: Lawrence Walker <lgwalker_at_look.ca>
Date: Tue Oct 10 01:24:10 2000

> > The whole port thing on the Mac is a real can of worms. On
>
> For some odd reason serial ports are always a can of worms. My
> standard 'algorithm' for hooking up an RS232 device is something like
> :
>
> 1) Read every fine manual associated with the device.
>
> 2) Notice that these manuals are written in a confusing way (as an
> example at least one manual uses 'transmitter protocol' to mean an
> ETX/ACK handshake and 'receiver protocol' to mean XON/XOFF handshake,
> no matter if they're applied to the send or receive functions of the
> device (!)).
>
> 3) Configure the device to be at least moderately sane
>
> 4) Hook it up to a terminal that uses data leads only and a breakout
> box. Fiddle with the hardware handshake lines to find out if they
> behave anything like how the manual describes them. Find out how to
> make it stop setting and how it tells the other device to stop
> sending. Some printers use pin 11 (of a DB25) for busy/ready, for
> example...
>
> 5) Wire up a custom adapter to put the signals on sane pins.
>
> 6) Try it out
>
> 7) Go back to 5 and repeat until it works
>
> 8) Label the adapter and hope it stays with the strange device....
>
 ROTFL. I'll have to keep this beside my bench to inject a bit of
humor and perspective the next time I'm ready to do serious
damage to either the equipment or myself.

> There are DEC serial ports that have no hardware handshaking at all.
> There are HP machines were the hardware handshake is sufficiently
> strange that I'd love to know what the designer was thinking about.
> There are printers with the ready signal on a strange pin. And so on.
> No 2 manufacturers do it the same way.
>
> FWIW it _is_ a DE9.
>
> > My PowerMac gives these specs:
>
> This sounds like it's designed to connect to some special Apple device
> (most async devices don't use external clocking, for example) rather
> than a normal device like a printer or a modem.
> >
> > 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)
>
 These were right from the Apple PPC manual specs for the serial
modem port. "Keep 'em confused and they'll keep coming back".

> -tony
>
 ciao larry



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Received on Tue Oct 10 2000 - 01:24:10 BST