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INPUTIOUTPUT PROVISIONS
26.2 -- Device Independent I/O
* *
CONTROLLER DESCRIPTOR BLOCK (COB)
*
HR$CDB EGU
FDB
FDB
FDB
FCB
FCB
FDB
FDB
*
o
. CDBlee
HRDRV$
CDBSDA
SE404
CDBHAD
DO$RES+DD$INP+DD$OCF
GDBDDF
VDSNFF+VD$BIN . CDSVDT
o
CDBDDA
o
.
CDBWST
LogicallYJ the paper tape reader should not
be
accessed
by
multiple
IDCBs
at
the
same time.
Thusl
the
device
is
considered to be reservable (Bit
"R"
oT
CDBDDF
set
to
1>-
The
paper
tape
reader is an input device only.
ThererOrEb
bit
"a"
of
CDBDDF
is
zero and bit "I" is one.
The
paper tape
reader is sensitive to end-of-rile records.
Thus,
it must be
a rile-type device (Bit "F" of
CDBDDF set to 1),
Bits
Ifw
lt
,
US",
and
ilL"
are
all zero
~ince
the paper tape reader is not
reUJindable (according to the definition in section
26.2.1. 4),
is not the system consolel and is not able to perform logical
sector
110.
The
de~ault
binary format has
been
arbitrarily
identified as binary record.
The
paper
tape
reader is capable of being used in the
non-file format mode and is capable of transmitting
eight~bit
data
to
the
device.
Thus,
both
bits
"N"
and
liB"
oT
CDBVDT
are set to one.
The only other required field of the CDB is the
address
of
the device driver
in
CDBSDA.
The remainder of the CDB is
reserved for expansion or is used
fo~
working storage by
the
device
driver.
Next,
the
device
driver itself
is
shown.
Of
the five
entry points that are required
by
each
device
driver,
only
two
are
used
for
the paper tape reader driver.
The other
three (device on, device ooFf,
and
device
termination)
are
dumm~
vectors
that
set a "no error" return status and then
return to the 1/0 function.
Page
26-11
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