Re: [hatari-devel] PSG and Centronics (parallel port)

[Thomas Huth <th.huth@xxxxxx>]

Am Sat, 04 Jul 2015 00:26:12 -0400
schrieb "Roger Burrows" <rfburrows@xxxxxxxxx>:

> I'm trying to figure out Centronics port handling on real Atari
> hardware, so I thought I'd check PSG handling in Hatari.  I browsed
> the psg.c module online and the comments indicate that if bit3 of PSG
> portA is set, the Centronics port is in input mode (although the code
> does nothing in this case anyway).  Is this correct, and is this
> documented anywhere (else :-)) ?

Not sure whether this is correct - it might have been derived from the
memory map document by Joerg Hohwiller, but sometimes these documents
are wrong, too.

> Assuming this is correct, am I right in believing that it would only
> apply to the Falcon?  I think that earlier machines didn't support a
> bidirectional parallel port, and this bit is an RS232 pin on those
> machines.

Earlier machines definitely had a bidirectional parallel port! You
could use it to add additional joysticks, for example (4 player
Gauntlet 2 was really cool).

Looking at the Atari Profibuch, it rather seems to me that you have to
use register 7 of the PSG to switch the centronics port from output to
input and vice versa.

 Thomas