Read Direct
(ROD)
General Description
Format
(SI)
Condition Code
Interrupt
Action
Privileged
Instructions
• The eight-bit I field specifies one of up to
five
possible sets
of
Direct
Control
trunks
to be sampled. The sampled eight-bit byte is
transferred
to
the
main
memory location specified by the first address (B1/D
1
)
from
the
Static
In
lines.
85
o
7 8
• Unchanged.
•
Privileged operation.
Address
error:
Addressing.
Protection.
15
16
19
20
Operation code
trap
(if
Direct Control option is
not
installed).
31
Notes • 1.
Each
of
the six Direct Control
trunks
has a
set
of
Direct
In
lines
which
are
sampled according to
the
following
pattern:
I-Field
Trunk
Sampled
Bit
0 = 1
Six
Bit
1.
=
1.
Five
Bit
2 =
1.
Four
Bit
3 = 1
Three
Bit
4 = 1
Two
Bit
5 = 1 One
Bit
6 = 0 Unused
(Must
be zero)
Bit
7 = 0 Unused
(Must
be zero)
The
program
must
specify only one I-Field
bit
set
to 1, otherwise
results of
the
instruction
are
unpredictable.
2.
A processor cannot Read Direct to itself. The I-Field
bit
associated
with
the receiving processor
must
always be
reset
to zero. (This is
a
programming
restriction.)
3. This instruction may be prolonged by the presence of a
HOLD signal.
If
so,
timer
updating may be skipped. However,
I/O
servicing will
not be affected.
119
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