Start Device
(SDV)
General
Description
Format
(SI)
Condition
Code
Interrupt Action
Notes
Privileged
Instructions
• The contents of the general register specified by Bl
are
added to
the
Dl
field. The
resultant
sum identifies
the
channel and device to which
the
instruction applies. These
are
specified by
bit
positions
21
through
31
of
the
sum. The I-field is not used and
must
be zeros.
The channel address word in main memory location 72 contains
the
protection key to be used and
the
address
of
the
first channel command
word. The channel command word designated by
the
channel address word
specifies
the
operation to be performed,
the
main memory
area
to be used,
and
the
action to be taken when
the
operation is completed. The condition
code indicates the result
of
the instruction.
9C
o
7 8
15
16
19
20
31
• 0 -
input/output
operation initiated
and
channel proceeding
with
execution.
1 -
status
bits stored in scratch-pad memory.
2 - busy
or
interrupt
pending.
3 - inoperable.
(For
a detailed description of the condition code settings, see Notes
below.)
• Privileged operation.
• 1. The address portion of
this
instruction specifies
the
device
and
channel
as
follows:
Bit
Positions
Channel
Specified
21
22 23
0
0
0
Multiplexor
0 0
1 Selector No. 1
0 1
0 Selector No. 2
0 1 1
Selector No. 3
1 0 0 Selector No. 4
1 1
0
Undesignated
Bit
positions 24 through
31
specify one of 256 possible devices.
2. The
standard
device byte
and
the
channel
status
byte stored by
the
previous
input/output
instruction in scratch-pad memory
are
destroyed
if
the
condition code
at
the
completion
of
the
Start
Device
instruction is
0
or
1.
3.
Status
storage (channel
status
byte
and
standard
device
byte),
if
required, occurs before
the
Start
Device instruction terminates.
4.
Condition Code 0 is
set
under
the following conditions:
108
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