Intel MCS48 User Manual page 317

8255A/8255A-5
CONTROL
WORD
#12
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
10
110
-H-
PA
7
-PA„
/i
PC
3
PC
-f
PB7-PB
CONTROL
WORD
#14
D
7
D
6
D
5
D,
D
3
D; D, D„
10
110
10
/
PA
7
.PA„
PC
3
PC
CONTROL
WORD
#13
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
CONTROL
WORD
#15
110
D
7
D
6
D
5
D
4
D
3
D
2
D,
D
10
110
11
/
PA
7
PA„
«
/
PC
7
-PC
4
/
"
PA
7
PA„
-/-
PCj-PC,
L
^ /±
PC
3
-PC
/
PBjPBo
/
PBjPBo
Operating
Modes
MODE
1
(Strobed Input/Output).
This functional con-
figuration provides a
means
for transferring
I/O
data
to
or
from a
specified
port
in
conjunction with strobes
or
"handshaking"
signals.
In
mode
1
,
port
A
and
Port
B use
the
lines
on
port
C
to
generate
or accept these "hand-
shaking"
signals.
Mode
1
Basic Functional
Definitions:
•
Two
Groups (Group
A
and
Group
B)
•
Each group
contains one
8-bit
data port
and one
4-bit
control/data
port.
• The
8-bit
data port can be
either
input or output.
Both
inputs and
outputs
are latched.
•
The
4-bit
port
is
used
for control and
status
of the
8-bit
data
port.
8-27
00744A