Intel 80C196NU ユーザーズマニュアル
7-8
8XC196NP, 80C196NU USER’S MANUAL
7.2.3
Bidirectional Port Pin Configuration Example
Assume that you wish to configure the pins of a bidirectional port as shown in Table 7-7.
To do so, you could use the following example code segment. Table 7-8 shows the state of each
pin after reset and after execution of each line of the example code.
pin after reset and after execution of each line of the example code.
LDB
Px_DIR,#00011111B
LDB
Px_MODE,#00000000B
LDB
Px_REG,#10010011B
Table 7-6. Control Register Values for Each Configuration
Desired Pin Configuration
Configuration Register Settings
Standard I/O Signal
P
x
_DIR
P
x
_MODE
†
P
x
_REG
Complementary output, driving 0
0
0
0
Complementary output, driving 1
0
0
1
Open-drain output, strongly driving 0
1
0
0
Open-drain output, high impedance
1
0
1
Input
1
0
1
Special-function signal
P
x
_DIR
P
x
_MODE
†
P
x
_REG
Complementary output, output value controlled by peripheral
0
1
X
Open-drain output, output value controlled by peripheral
1
1
X
Input 1
1
1
†
During reset and until the first write to P
x
_MODE, the pins are weakly held high.
Table 7-7. Port Configuration Example
Port Pin(s)
Configuration
Data
P
x
.0, P
x
.1
high-impedance input
high-impedance
P
x
.2, P
x
.3
open-drain output
0
P
x
.4
open-drain output
1 (assuming external pull-up)
P
x
.5, P
x
.6
complementary output
0
P
x
.7
complementary output
1