Chapter
3.
Instruction
Set
RP
RPE
3-52
RETURN
IF
POSITIVE
The
RP
instruction tests th(' sign flag. If the flag
is
reset
to
zero to indicate positive ddta
in
the accumuldtor,
the instruction
pop,
two byte';
off
the stack and places them
in
the program
counter.
Program
execution
resumes
at
the new dddress
in
the progrdm counter.
If
the
fhg
is
set
to
one, progrdm
execution
simply
continues
with the next sequential in5.trunion.
Op co de Operand
RP
Operdnds dre
not
permitted
with the
RP
instruction.
Cycles:
Std
tes:
Addressing:
Fldgs:
Example:
o 0
~
or 3
5 or
11,
(6
or
12
on 8085)
register indirect
none
For the sdke
of
brevity, an example i, given for the RET irl'>truction but not for each
of
II'>
clo,ely related
vdriants.
RETURN
IF
PARITY
EVEN
Pdrity i, even if the byte
in
the
accumulator
has an even number
of
one bits.
The
pdrity flag
is
set
to
one
to
indicate this
condition.
Thl' RPE dnd RPO
imtructiom
are useful for testing the parity of
input
ddtd. However,
the
IN
instruction does not set any
of
the condition flag,. The flags
Cdn
be
set
without
altering the ddta by
ddding
OOH
to
the content'·,
of
the
accumulator.
The RPE
imtruction
te,ts
the parity flag. If the
fldg
is
set
1.0
one to indicate even pdrity, the instruction pops
two
byte,
off
the stack and pldce,
them
in
the progrdm counter. Program
execution
resumes
,1t
the new
dddrcS'>
in
the program counter.
If
the
fldg
is
zero, program
execut,on
simply
continue,
with the next ,equential
imtruc·
tion.
Opcode
Operand
RPE
Operands are
not
permitted with the RPE instruction.
I
'--
1
___
0
__
0_~
Cycles:
Sta
tes:
Addre'>5ing:
Flags:
or 3
5 or
11
(6
or
12
on 8085)
register indirect
none
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