| RE: [hatari-devel] Re: ACSI issue with Hatari |
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> From: Troed Sangberg
> Sent: 3 October 2014 19:39
> To: hatari-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [hatari-devel] Re: ACSI issue with Hatari
>
> > first, then the higher address. So this driver has definitely a bug.
> >
>> I think this just works "by accident" with other emulators and real
> > hardware, e.g. because in real hardware there might be a small delay
> > within the device or so.
> Well. If it works on real hardware then that is the expected behaviour and there's no bug in the driver.
> (semantics, but important)
> /Troed
Roger Burrows just has thrown light on that case:
http://dev-docs.atariforge.org/files/ACSI_DMA_Guide_6-28-1991.pdf
DMA CHIP ANOMALY - It is possible to get a double strobe from the DMA chip it the
DMA Mode Control Register is not written to immediately after the DMA Data Port. For
this reason. while writing to the DMA Data Port it is necessary to write the DMA Mode
Control operation for the next operation. This can be done by writing a long word to the
Date Port with the data in the upper word and the next operation in the lower word.
See the move.l in the programming examples in chapter 4 for an example of how to do
this. This restriction only applies to the writing of the DMA Data Port and not to the
writing of the DMA Mode Control Register.