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INSTRUCTION
SET
Note: A 12-bit address
specification
does
not
cause an
error
if
the
DJNZ
instruction
and
the
jump
target
are
on
the
same page. If the
DJNZ
instruction
begins in
location
255
of
a page, it must
jump
to
a target
address on
the
following
page.
Example:
Increment
values in data
memory
locations
50-54.
MOV
RO,#50
;MOVE '50' DEC
TO
ADDRESS
;REG 0
MOV
R3,#5 ;MOVE '5' DEC
TO
COUNTER
;REG 3
INCRT:
INC
@RO
;INCREMENT
CONTENTS
OF
;lOCATION
ADDRESSED BY
;REG 0
INC
RO
;INCREMENT
ADDRESS IN REG 0
DJNZ
R3,
INCRT
;DECREMENT REG 3 -
JUMP
TO
;'INCRT' IF REG 3
NONZERO
NEXT - ;'NEXT'
ROUTINE
EXECUTED
;IF
R3
IS ZERO
EN
I Enable External Interrupt (Not in 8021)
10000101011
External
interrupts
are enabled. A
low
signal on
the
interrupt
input
pin initiates the
interrupt
sequence.
EN
TCNTI Enable Timer/Counter Interrupt (Not in 8021)
10010101011
Timer/counter
interrupts
are enabled. An
overflow
of
the
timer/counter
initiates
the
interrupt
sequence.
ENTO
ClK
Enable Clock Output (Not in
8021,8022)
10111101011
The test 0
pin
is enabled
to
act
as
the
clock
output.
This
function
is disabled by a system reset.
Example: EMTSTO: ENTO
ClK
;ENABlE
TO
AS
CLOCK
OUTPUT
IN A,Pp Input Port or Data
to
Accumulator
10000110ppi
This
is
a
2-cycle
instruction.
Data
present
on
port
'p'
is
transferred
(read)
to
the
accumulator.
In
the
8021
IN
A,P2
inputs
P20-P23
to
AO-A3
while
A4-A7
is
set
to
zero.
(A).-.
(Pp) p=1-2
Mnemonics
copyright
Intel
Corporation
1976.
4-16