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 Post subject: FDS disk reading
PostPosted: Fri Apr 21, 2006 4:23 pm 
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Joined: Mon Sep 27, 2004 2:13 pm
Posts: 1667
Location: .ma.us
Could somebody instruct me through an entire disk read? (With CRC)

This is what I've gathered:

-Make sure disk is in drive and it's powered ($4032.0 = 0, $4033.7)
-Turn motor on and put in read mode ($4025.1 = 0, $4025.2 = 1)
-Wait for byte transfer flag ($4030.1 = 1)
-Check if CRC passed ($4030.4 = 0)
-Read data... repeat until $4032.1 = 1

Does "turn motor on" initiate a complete read cycle?

$4025.6 sounds important, but why I'm not sure. What's the "GAP period"? Is this necessary for reading byte level or only "blocks"?

Is there a way to read the full disk (access data "randomly", in sequence :) through the BIOS?


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