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OTHER
SYSTEM FUNCTIONS
27.4 -- Diskette File Functions
Pseudo
~egiste~
Contents
P
5
v
,..
A~B,C
Y
U=S
DP=O
Starting execution address
See description of
S
above.
Contents
vary
depending on load mode.
Starting load address.
Ind etermi nate.
Indeterminate (MDOS09)
1'100509
only
MDOS09
only
This
feature facilitates
sta~ting
the execution
or
a
p~ogram
from the debug monitor since the starting
execution
address
n~ed
not be remembered
by
the operator;
however~
caution must
be exercised if
prog~ams
are loaded into the User
Memor~
Map
of
an
EXORciser
II
with
the
dual
memory
map
configured.
Since the stack
pointe~
contains
the
address
of
the
last
loaded
program
location,
use of the debug commands ";PH or
.. iNn
wi
11
cause
seven
locations
of
the
pT'ogT'am
to
be
destroyed.
This
may
alte~
program data
O~
instructions.
It
is recommended that the stack pointer first
be
changed
via
the
.. ;
SU
commandi
that
the
"nnnn;
Gil
command
be used to
initiate execution;
or that stack
area be provided at the end
of
the
program
a~ea.
Fo~
programs not loaded into the User
Memory Map of an EXORciser
I I
system with the dual
memo~y
map
con
oF
i
9
ur
e
d
I
t his pre cal( t ion
doe
s not a p ply.
Pa~ticular
attention
should be placed on programs that
load into
the
highest
memory
address
$FFFF.
Since
the
diskette
controller
can only load programs in a multiple of
eight bytesl
such
programs
should
have. a
starting
load
address
that
is
a
multiple
of
eight.
Otherwise,
the
calculated ending load address
will
be
greater
than
$FFFF,
causing an error.
Caution
must
also
be
exercised
if
MOOS
is
to
be
reinitialized
f~om
the debug monitor after
having
loaded
a
prog~am.
The
ABORT
or
RESTART
pushbuttons mu-st first be
depressed before the debug
command
"EBOOiG"
or
"MDOS"
is
executed.
27.4.4 Allocate diskette space -- . ALLOe
The
.ALLOe
function
allocates
contiguous segments of
diskette space for a file.
The file's
Ret~ieval
Information
Block
and
the system's Cluster Allocation Table are updated
to account
ro~
the allocated space.
Since
space
allocation
is
performed
automatically
by
the
device independent I/O
functionsl
the
.ALLOe
function
should
only
be
used
by
progT'ams
that
are
doing
physical
sector
lID
on
MDOS
compatible diskettes.
Page
27-25
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