Execute
(EX)
General Description
Format
(RX)
Condition Code
Interrupt
Action
Branching In8truction8
• The instruction in the location specified
by
the
second address
(X
2
/B
2
/D
2
)
is modified by
the
contents
of
the
register
specified by
the
first
address
(R
1
).
Then,
the
modified instruction is executed
and
control is
returned
to
the
instruction following
the
Execute instruction.
o
7 8 11 12 15 16 19 20
31
• May be
set
by
the
instruction being modified
and
executed.
• Address
error:
Addressing.
Specification.
Notes • 1. Bits 8-15
of
the
subject instruction
are
"OR"ed
with
bits
24-31
of
the register specified by
the
first address
(R
1
).
2.
If
Rl
is
zero, no modification takes place.
3. The ILC is set to two (length
of
the
Execute)
and
the
P counter
is set to the address
of
the instruction following
the
Execute
instruction.
4.
The contents
of
Rl and the subject instruction
in
main
memory
are
unaltered.
5.
Interrupts
are
inhibited until
the
subject instruction has been
completed.
6.
When
the
subject instruction is a successful branching instruction,
the
P counter is updated by
the
branch address.
200
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