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APPENDIX
D.
Diskette Cont'1'oller Entry Points
The floppy diskette controller module firmware
is
used
to
control
all
of
the EXORdisk
I I / I I I
ha~dware
functions.
The
entry points to the various runctions
a~e
desc'1'ibed
in
this
section.
Parameters required
by
the firmware functions
are stored in
RAM
in the locations descl'ibed by the following
table:
Name
Addl'ess Definition
CURDRV
$0000
STRSCT
SOOOl
NUMSCT
$0003
LSCTLN
$0005
CURADR
$0006
FDSTAT
$0008
This
byte
contains
~ne
Dlnary logical
unit numbel' of the drive to
be
selected
(zel'O thl'ough three).
These
two
bytes
contain
the
physical
sector numbel' of the first sector
to
be
used (starting sector).
These
two
b~tes
contain
the number of
sectors to be used.
This number includes
a
partial
sector}
ir
a partial sector
read is
being
requested.
The
sum
of
STRSCT
and NUMSCT cannot be greater than
$7D2
(single-sided
diske~tes)
01"
$FA4
(double-sided diskettes).
This
byte contains the number of bytes to
be read from the
last
sector
during
a
read
operation.
This number should be a
multiple of eight and cannot
be
greater
than 128
($80>.
If
a numbel' is specified
that is not a multiple
of
eightl
the next
large~
multiple
oT
eight
by~es
~ill
be
read.
These two bytes contain the rirst address
in
memory
that
is
to be used during a
T'ead OT'
w~ite
operation.
This
location
is
updated
after each sector is read or
. written.
During UlT'ite
test
operationsl
these
two bytes contain the address of a
two-byte data buffer.
This byte contains a status indication of
the
performed
function.
If
an
error
occurred during a diskette operation, the
carry
bit in the condition code register
Page
D-01
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