RANA Systems Elite Controller, User Manual

Page: 324 / 328

ELITE SERIES USER MANUAL APPEN. C - CP/M NOTES
The [IX] register will return pointing to the
slot number times 16 for the controller to which
drive [C] is attached. The drive number of
drive [C] on that controller card will be at
[IX]+16. These values are within a drive
mapping table described below.
The [IY) register will return pointing to drive
[C]’s seek table entry. The seek table is also
described below. I m p o r t a n t : The seek table is
located in the alternate bank of the ramcard
(remember, 56K system required). The alternate
bank of the ramcard will normally be mapped-out
(primary bank mapped-in) whenever the BIOS is
not in control of the system (since its the only
one expecting an alternate bank). To access the
seek tables, the alternate bank must be mapped-
in and then back out while leaving the ramcard
write enabled.
C . 2 . D r i v e M a p p i n g T a b l e
The original Apple II CP/M as distributed by
Microsoft assumed that there were. only two
drives for every controller card it found in the
Apple. This allowed the BIOS to do some quick
and simple math to calculate where it could find
the physical drive (slot and drive number)
associate with CP/M’s logical drive (A:—P:).
Since the Rana enhancements take into account
any combination of Rana four-drive Elite
Controllers and Apple two-drive Disk II
controllers, quick and simple math was no longer
P a g e C - 3