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INPUTIOUTPUT FUNCTIONS
25.2 -- Device Dependent
1/0
Functions
START
LDAA
#SPACE
INITIAL CHAR
LOOP
LDX
#OBUFF
LDAB
#80
SCALL
· STCHR
FILL BUFFER
SCALL
· PRINT
PRINT THE STRING
INCA
BUMP CHARACTER
CMPA
#RUBOUT
END OF DISPLAYABLE SEGUENCE
BNE
LOOP
SCALL
· MDENT
EXIT TO MDOS
*
*
WORKING STORAGE
*
OBUFF
BSZ
80
OUTPUT
BUFFER
FeB
CR
BSZ
80
5TAC~
SET HERE
BY LOAD
'*
END
START
BEGIN EXECUTION
AT
THIS LABEL
25.2.5 Physical sector input -- . DREAD,
.EREAD
The. DREAD and . EREAD functions are both used to read
a
single
physical
sector
from
the diskette into a specified
buffer.
For multiple physical sector
in~ut
the functions
in
section
25.2.7
should be used.
The. DREAD function will only
return to the
calling
program
if
no
diskette
controller
errors
are
detected
during
the
read attempt.
The .EREAD
function,
on the other
hand,
wi
11
return
to
the
call ing
program
whether
an
error
occurred
or
not.
The. EREAD
function will return the error status that
was
detected
by
the diskette
controller~
In
either
casel
if
a
diskette error occurred that was
,... e t,..
y
a
b 1
e (
eRe,
del e ted d a t a
ma r
k ,
d a t a
add res s
ma r
k
l o r
address
mark
eRe
errors), the following steps
were
taken in
an attempt to recover from the error:
1.
The
sector
was
reread
five
times
without
repositioning the read head.
2.
The
read
head
was
stepped
outward
(towards
cylinder
zero)
a
maximum
of
five
cylinders,
repOSitioned
over
the
cylinder
in
which
the
sector to be read resides, and another five
read
attempts were performed.
3.
The
read
head
was
stepped
inward
(totdards
cylinder
76)
a
maximum
of
five
cylinders,
repositioned
over
the
cylinder
in
which
the
sector to be re.ad resides, and a.nother five
read
attempts were performed.
If
an
error
occurs
during
the
. DREAD function,
the
Page
25-09
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