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INPUT/OUTPUT
PROVISIONS
26.2 -- Device Independent I/O
N (Bit 7) -- Non-file format rlag
This bit indicates
whethe~
O~
not the device can
be
used
to perform
FDR
processing.
Certain devices
(i. e.,
those with the file-type bit set
to
zero
in
CDBDDF)
can
never
perform FDR processing; however,
devices which are
file-type
devices
can,
in
some
cases,
be
used
in
eithe~
the
Tile format
or
the
non-file format mode (see IOCDTT description,
section
25.3.1.2>'
If
the
liN"
bit is set to one,
then the
device can be used in the non-file Tormat
mode.
If
the
flNfI
bit is set to zero,
then the device cannot be
used in the non-file format mode.
The diskette drive
is
an
example
of
a
device that can only be used in
the file rormat
mode.
The
console
reader
is
an
example
of a device that can be used in either mode.
The line printer is an example
aT
a device
that
can
only be used in the non-file format mode.
NOT USED (Bits 3-6, 0-1)
Reserved area
These
bits
of the CDaVDT byte are
~eserved
for
future expansion.
They must be zero.
B
(Bit
2) --
Binary device flag
This bit indicates whether a device can
process
eight-bit
data
or
not.
If the
IIBu
flag is set to
one,
then eight-bit data are valid.
If
the "a
tl
flag
is set to zero,
then eight-bit data are invalid.
26.2.1.6
CDBDDA -- Device dependent area
These
two-bytes
of the
CDB
are available to the device
drivers as working storage.
For the MDOS-supported
devices,
this field has been provided for future expansion.
For other
devices,
this field can be used
ror
whatever
purposes
are
deemed appropriate.
26. 2. 1. 7
CDBWST -- Wor king s torag e
These
two-bytes
of the
CDB
are available to the device
d~ivers
as working storage.
26.2.2 Device drivers
Each device type that is to be.accessed via
the
.device
independent
IIO
functions
(section 25.3) must have its own
d~iver
program.
All device drivers must
be
accessible
for
the following five functions:
j
Page
26--08
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