Execute (Ex) - RCA 70/46 Reference Manual

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