10 Apr
2007
10 Apr
'07
5:35 p.m.
On Tue, 10 Apr 2007, Christian Corti wrote:
Ok, I was referring to the IBM 5114 maintenance manual
which describes FM
and MFM encoding that IBM used for their drives/controllers. But you are
right, e.g. the "Floppy Disk Data Separator Design Guide for the DP8463" says
that the address mark $A1 has a clock pattern of $0A. I don't really know
what IBM meant with "missing clock bits 2, 3 and 4"... I think it applies
to the $FE or $F8 address mark in FM.
While you are at it, notice that the 1771 can create some FM data address
marks that the 179x can not. Worse yet, they are used in TRS80 (model 1)
disk formats.