Intel MCS48 User Manual page 346

8259A
PIN
FUNCTIONS
Name
I/O
Pin #
Function
Vcc
28
GND
14
D
-7
I/O
11-4
IR0-7
I
18-25
RD
WR
INTA
26
+ 5V
supply.
Ground.
Bidirectional
data bus,
used
for:
a)
programming
the
mode
of the
8259A (programming
is
done by
software);
b)
the
microprocessor
can read the status
of
the
8259A;
c)
the
8259A
will
send
vectoring
data to the
microprocessor
when
an
interrupt
is
acknowledged.
Interrupt
Requests:
These
are
asynchronous
inputs.
A
positive-
going
edge
will
generate an
in-
terrupt request.
Thus
a request
can be generated by
raising
the
line
and
holding
it
high until
acknowledged,
or
by a negative
pulse.
In level
triggered
mode, no
edge
is
required.
These
lines
are
active
HIGH.
Read
(generally
from 8228
in
MCS-80
system
or
from 8086
in
MCS-86
system).
Write
(generally
from 8228
in
MCS-80
sytem
or
from 8086
in
MCS-86
system).
Interrupt
Acknowledge
(generally
from 8228
in
MCS-80
system,
8086
in
MCS-86
system).
The 8228
generates
three distinct
INTA
pulses
when
a
CALL
is
inserted,
the 8 086 produces two
distinct
INTA
pulses during an
interrupt
cycle.
CS
A0
INT
C0-C2
I/O
SP/EN
I/O
1
Chip
Select:
RD
and
WR
are en-
abled by
Chip
Select,
whereas
Interrupt
Acknowledge
is
Inde-
pendent
of
Chip
Select.
27 Usually the least significant bit
of
the
microprocessor address
out-
put
(A1
in
MCS-86
system).
When
A0=1
the
Interrupt
Mask
Register
can be loaded
or read.
When
A0
=
the
8259A
mode
can
be
programmed
or
its
status
can
be
read.
CS
is
active
LOW.
17
Goes
directly to
the
micro-
processor interrrupt input.
This
output
will
have high
V
h
to
match
the
8080
3.3V
V,
H
-
INT
is
active
HIGH.
12
Three cascade
lines,
outputs
in
13
master
mode
and
inputs
in
slave
15
mode. The master
issues the
binary
code
of
the
acknowledged
interrupt level
on
these
lines.
Each
slave
compares
this
code
with
its
own.
16
SP/EN
is
a dual function
pin. In
the buffered
mode SP/EN
isused
to
enable bus
transceivers
(EN). In
the non-buffered
mode
SP/E"N
determines
if
this_8259A
is
a mas-
ter
or a
slave.
If
SP=
1
the
8259A
is
master;
SP =
indicates
a
slave.
ABSOLUTE MAXIMUM
RATINGS*
Ambient Temperature Under
Bias
-
40 °C
to
85 °C
Storage Temperature
-
65 °C
to
+ 150°C
Voltage
On
Any
Pin
With Respect
to
Ground
-
0.5V
to
+ 7V
Power
Dissipation
1
Watt
D.C.
CHARACTERISTICS
T
A
= 0°C
to
70
°C,
V
CC
=5V±
10%
(8259-
A),
V
CC
=5V±
10%
(8259A)
'COMMENT
Stresses
above those
listed
under "Absolute
Maximum
Ratings"
may
cause permanent damage
to
the device. This
is
a stress
rating
only
and
functional operation
of
the device
at
these
or
any other conditions above
those
indicated
in
the operational sections of this specification
is
not
implied.
Symbol
Parameter Min.
Max.
Units
Test Conditions
VlL
Input
Low
Voltage -.5
V
V|H
Input
High Voltage
2.0
V
CC
+.5V V
Vol
Output
Low
Voltage .45
V
l
0L
=
2.2
mA
Voh
Output High Voltage
2.4
V
l
0H
=
-400
M
A
VoH(INT)
Interrupt
Output High
Voltage
3.5
2.4
c
V
l
0H
=
-100
M
A
l
0H
=
-400
mA
'LI
Input
Load
Current
10
M
A
V|
N
= V
cc
to0V
!lol
Output Leakage
Current
-10
MA
V
OUT
=0.45V
'cc
V cc Supply
Current
85
mA
'lir
IR
Input
Load Current
-300
10
fA
M
A
V,n
=
V,n
= V
cc
8-56