Re: [cc65] dio_query_sectcount() on Atari ?

From: Fatih Aygün <cyco1301yahoo.com>
Date: 2012-10-24 10:54:46
Sorry for the last mail without content.

>Well, this is likely why Christian didn't implement this function on the

>Atari.  There's no good method to quickly determine the number of sectors on
>a disk. :)


I believe there is:

1 - Read the 4th sector. (the xf551 drive had a bug, it returned the wrong PERCOM info after reading the normally 128-byte boot sectors, a read from sector 4 eliminates this chance)

2 - Read status (SIO command 0x53) and save that info.

3 - Request a PERCOM block. If it succeeds use that information.

4 - If reading PERCOM block fails assume 1050, 810 (or even 815) or compatible. Use the status byte 0 to differentiate between single, enhanced (medium) and double density. (bit 5 is set if double density and bit 7 is set if enhanced density). If we're only looking for sector count, only the bit 7 matters.

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Received on Wed Oct 24 10:55:02 2012

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