Filter
Top Products
inter
8080Al8080A·1/8080A·2
INSTRUCTION SET
The
accumulator
group
instructions include arithmetic and
logical
operators
with
direct, indirect, and immediate ad-
dressing modes_
Move, load, and
store
instruction groups provide
the
ability
to
move either 8
or
16 bits
of
data
between memory,
the
six working registers and
the
accumulator
using direct,
in-
direct, and immediate addressing modes.
The
ability
to
branch
to
different
portions
of
the
program
is
provided
with
jump,
jump
conditional, and
computed
jumps. Also
the
ability
to
call
to
and return from sub-
routines
is
provided
both
conditionally and unconditionally.
The
RESTART (or single
byte
call instruction)
is
useful for
interrupt
vector
operation.
Double precision
operators
such as stack manipulation and
double
add
instructions
extend
both
the
arithmetic
and
interrupt
handling capability
of
the
8080A.
The
ability
to
Data and Instruction Formats
increment and
decrement
memory,
the
six general registers
and
the
accumulator
is
provided
as
well as
extended
incre-
ment
and
decrement
instructions
to
operate
on
the
register
pairs and stack pointer.
Further
capability
is
provided
by
the
ability
to
rotate
the
accumulator
I~ft
or
right
through
or
around
the
carry
bit.
Input
and
output
may be accomplished using
memory
ad-
dresses as I/O
ports
or
the
directly addressed I/O provided
for
in
the
8080A
instruction set.
The
following special instruction group
completes
the
8080A
instruction set:
the
NOP instruction, HALT
to
stop
pro-
cessor
execution
and
the
DAA instructions provide decimal
arithmetic
capability. STC allows
the
carry flag
to
be di-
rectly set, and
the
CMC
instruction allows it
to
be comple-
mented.
CMA
complements
the
contents
of
the
accumulator
and XCHG exchanges
the
contents
of
two
16-bit register
pairs directly.
Data
in
the
8080A
is
stored
in
the
form
of
8-bit binary integers. All
data
transfers
to
the
system
data
bus will be in
the
same format.
I
D
7
D6
D5
D4
D3
D2
D1
Dol
DATA WORD
The
program instructions may be one,
two,
or
three
bytes
in
length. Multiple
byte
instructions
must
be stored
in
successive words
in
program memory.
The
instruction formats
then
depend on
the
particular
operation
executed.
One
Byte Instructions
I
D7
D6 D5 D4
D3
D2
Two
Byte Instructions
I
D7
D6 D5 D4
D3
D2
I
D7
D6
D5 D4
D3 D2
Three Byte Instructions
I
D7
D6
D5 D4
D3
D2
I
D7
D6 D5 D4
D3
D2
I
D7
D6 D5 D4
D3
D2
DtYDJ
D1
Do I
D1
Do I
D1
Do
I
D1
Do I
D1
Do I
OP CODE
OP CODE
OPERAND
OP
CODE
LOWADDRESSOR OPERAND 1
HIGH ADDRESSOR OPERAND 2
TYPICAL INSTRUCTIONS
Register
to
register,
memory
refer-
ence, arithmetic
or
logical,
rotate,
return, push, pop, enable
or
disable
Interrupt
instructions
Immediate mode
or
I/O instructions
Jump,
call
or
direct load and
store
instructions
For
the
8080A
a logic
"1"
is
defined as a high level and a logic
"0"
is
defined as a low level.
6-7
AFN·OO735C