Channel
Status Byte
(Cont'd)
I
nputjOutput
Operation
the
condition code indicates
that
Status
is stored. The
bit
significance
of
the
channel
status
byte is as follows:
Bit
Position 8 is
the
program
controlled
interrupt
bit. When set,
this
bit
indicates
that
a Channel Command Word was accessed which
had
the
program
controlled
interrupt
flag
bit
set. A channel
interrupt
occurs
for
the
appropriate
channel while
the
input/output
operation specified by
the
Channel Command Word is being executed.
Note: The
program
controlled channel
interrupt
occurs
after
the
first
data
byte
has
been
transferred.
Bit
Position 9 is
the
incorrect
length bit. When set,
this
bit
indicates
that
when
the
input/output
operation was
terminated,
the
byte count
specified in the channel command was not equal to
the
number
of
bytes
received from,
or
sent
to,
the
input/output
device. The
incorrect
length
indicator can be
set
only
if
the
suppress
length
indicator
flag
bit
in
the
channel command word is
reset
to
o.
The following conditions cause
the
incorrect
length
bit
to be
set:
1. Count
High
on
Input
(Read, Read Reverse,
Sense).
The
main
memory
area
specified by
the
Channel Command Word is
not
com-
pletely filled by
transmission
from
the
device. The final
byte
count
in
Channel Command Register-II is
greater
than
zero.
2.
Count
High
on
Output
(Write,
Write
Control).
Data
in
the
main
memory
area
specified by
the
Channel Command Word is
not
com-
pletely
transferred
and
the
device
terminated.
The final
byte
count
in
Channel Command Register-II is
greater
than
zero.
Notes:
1.
If
incorrect
length
occurs
during
command
chaining
and
the
Suppress
Length
Indicator
flag
bit
of
the
current
command is reset,
the
incorrect length
bit
is set.
2.
If
incorrect length occurs
during
the
last
command
of
a
chain
(the
Chain
Data
flag
bit
is
reset),
and
the
Suppress
Length
Indicator
flag
of
the
command is set,
the
incorrect
length
bit
is
not
set.
Bit
Position
10
is
the
program
check bit. When set,
this
bit
indicates
that
a
programming
error
was detected by
the
channel.
The following conditions cause
the
program
check
bit
to be
set:
1. Invalid Channel Command Word Address.
The
addressed Channel
Command
Word is
not
located on a double
word
boundary.
2. Invalid
Channel Command Word Address.
The
addressed Channel
Command
Word is outside
the
available
main
memory
for
the
par-
ticular
installation.
3. Invalid
Data
Address. The
main
memory location specified by
the
data
address
in
the
Channel Command
Word
is outside
the
avail-
able
main
memory
for
the
particular
installation.
64
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