On Fri, 4 Aug 100 g.j.p.a.a.baltissen@kader.hobby.nl wrote: > Hallo, > > I know there has been some discussion about how you can tell a 8250 to go into > the 8050 mode. But what I don't know (missed, forgot) is how a 8250 recognizes > if it is dealing with an 8050 or an 8250 formatted disk. AFAIK that it simply > expects to read a 8250-disk and if it isn't, returns a read-error. > > The reason while I'm asking this is the fact that I'm devolloping the part of a > program which enables you to creat disk-images. I noticed that byte 3 of T/S > 18/0 was $80 for a 1571-disk indicating a double sided disk (0 for a 1541). > Then I noticed that there was no difference in the directory headers of a 8050 > or 8250-disk. So how is a disk recognized? The 8250 decides the format type by reading the BAM. When a disk is initialized, the BAM is read into a drive buffer. The 8050 has 2 BAM sectors and the 8250 has 4. Bytes 4 and 5 of each BAM sector specify the track range of that BAM sector. Byte 5 of BAM sector 2 can be used to quickly identify the format. The 8050 format has 78 there and the 8250 has 101. The routine that lets the 8250 write 8050 disks, modifies the drive's disk parameter table that specifies the number of BAM sectors and their location. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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