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INSTRUCTION SET
RETR
Return
With
PSW
Restore
(Not in 8021, 8022)
11001100111
This is a
2-cycle
instruction.
The stack
pointer
is
decremented.
The
program
counter
and bits 4-7
of
the
PSW are then restored
from
the
stack.
Note
that
RETR
should
be used
to
return
from
an
interrupt,
but
should
not
be used
within
the
interrupt
service
routine
as
it
signals
the
end
of
an
interrupt
routine
by
resetting
the
Interrupt
in Progress
flipflop.
(SP)..-
(SP)-1
(PC)..-
((SP))
(pSW
4-7)"-
((SP))
RL
A
Rotate
Left
Without
Carry
1
1
110101111
The
contents
of
the
accumulator
are rotated
left
one
bit.
Bit
7 is rotated
into
the
bit
0 position.
(An+1)"-
(An)
(AO)..-
(A7)
n=0-6
Example:
Assume
accumulator
contains
10110001
..
RLNC: RL A ;NEW
ACC
CONTENTS
ARE 01100011.
RLC
A
Rotate
Left
Through Carry
11111101111
The
contents
of
the
accumulator
are rotated left
one
bit. Bit 7 replaces
the
carry
bit;
the
carry
bit is
rotated
into
the
bit
0
position.
(An
+1)..-
(An)
(AO)--
(C)
(C)--
(A7)
n=o-S
Example: .
Assume
accumulator
conta,ins a 'signed' number;
isolate sign
without
changing
value.
RL TC: CLR
C ;CLEAR
CARRY
TO
ZERO
RLC A
;ROTATE
ACC
LEFT,
SIGN
;BIT
(7)
IS PLACED IN CARRY
RR
A
;ROTATE
ACC
RIGHT
- VALUE
(BITS 0-6) IS RESTORED,
;CARRY
UNCHANGED,
BIT
7
;IS ZERO
Mnemonics
copyright
Intel
Corporation
1976.
4·30