|Re: [hatari-devel] reading DMA sector count in HDC mode ?|
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Am Fri, 13 Dec 2013 00:52:52 +0100
schrieb Nicolas Pomarède <npomarede@xxxxxxxxxxxx>:
> I think the dma sector counter is common to FDC/HDC mode, so it
> should be the same, but could someone with a hard drive confirm this ?
I do not have an ACSI hard disk, but I think you're right ... the DMA
sector counter register belongs to the DMA chip, not the hard disk, so
I think it is the same for floppy and hard disk mode.
> None of the doc I have are clear on this, they don't mention if
> sector count can be read or not. But as dma status has a bit to tell
> if sector count is 0 or not, this could confirm you can't read sector
> count, you can only know if it reached 0.
I just had a look in my "Scheibenkleister" book (one of the best books
about Atari floppy and hard disks), and on page 179 I found this
"Leider kann man den Sektorzähler nur beschreiben, nicht aber lesen;
man kann nur an Bit 1 des DMA-Statusregisters ($FF8606, nur lesbar)
erkennen, ob der Sektorzähler mittlerweile bei Null angekommen ist."
"Unfortunately, you can only write to sector counter, but not read it;
you can only watch bit 1 of the DMA status register ($FF8606, read
only) to see whether the sector counter already reached zero."
Unfortunately, it is not mentioned whether there is a difference
between floppy and hard disk mode for the sector count register, but I
do not think that there is any.