|Re: [hatari-devel] PSG and Centronics (parallel port)|
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Am Sat, 4 Jul 2015 10:04:33 +0200
schrieb 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.
Looking at the schematics of the Falcon, it seems like the PSG port A
bit 3 is directly connected to the pin 17 of the centronics port
(that's the SELIN line). So this is not about switching the direction
of the data ports, it's just one additional pin on the centronics port
that was unused on the STs.