RCA 70/46 Reference Manual page 128

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.
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