CPO
Chapter 3. Instruction Set
The operand must specify the data to be compared. This data may
be
in
the form
of
a number, an ASCII
constant,
the label
of
a previously defined value, or an expression. The data may not exceed one byte.
The assembler's relocation feature treats
all
external and relocatable symbols
as
16-bit addresses. When one
of
these symbols appears
in
the operand expression
of
an immediate instruction, it must be preceded by either
the
HIGH or
LOW
operator
to specify which byte
of
the address
is
to
be
used
in
the evaluation
of
the
expression. When neither
operator
is
present, the assembler assumes the
LOW
operator
and issues an error
message.
Example:
J-----1.~
data
~
Cycles:
States:
Addressing:
Flags:
2
7
register indirect
Z,S,P,CY,AC
The instruction
CPI
'C' compares the
contents
of
the accumulator
to
the letter C (43H).
CALL
IF
PARITY
ODD
Parity
is
odd
if
the
byte
in
the accumulator has an
odd
number
of
one bit,. The parity flag
is
set
to
zero to
indicate this condition. The
CPO and
ePE
instructions are useful for testing the parity
of
input
data. However,
the
IN
instruction does not set any
of
the condition flags. The flags can
be
,e1
without
dltering the data
by
adding
OOH
to the
contents
of
the accumulator.
The
CPO instruction combines functions
of
the J
PO
and PUSH instructions. CPO tests the setting
of
the parity
flag.
If the flag
is
set
to
zero, CPO pushes
the
contents
of
the program
counter
onto
the slack and then jumps
to the address specified
by
the CPO instruction. If the flag
is
set
to
one, program execution simply continues
with the
next
sequential instruction.
Op co de Operand
CPO
address
Although the use
of
a label
is
more
common,
the address may also be specified as a number or an expression.
1
1 1
0 0
1
0
0
lowaddr
high addr
Cycles: 3 or 5
(2
or
:5
on 8085)
States:
11
or 17
(9
or 18 on 8085)
Addressing: immediate/register indirect
Flags: none
3-17
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