Intel 80C196NU, 8XC196NP Bidirectional Port Pin Configuration Example, Port Configuration Example

8XC196NP, 80C196NU USER’S MANUAL

Table 7-6. Control Register Values for Each Configuration

Desired Pin Configuration	Configuration Register Settings
Standard I/O Signal	Px_DIR	Px_MODE†	Px_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	Px_DIR	Px_MODE†	Px_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 Px_MODE, the pins are weakly held high.

7.2.3Bidirectional Port Pin Configuration Example

Assume that you wish to configure the pins of a bidirectional port as shown in Table 7-7.

Table 7-7. Port Configuration Example

Port Pin(s)	Configuration	Data
Px.0, Px.1	high-impedance input	high-impedance
Px.2, Px.3	open-drain output	0
Px.4	open-drain output	1 (assuming external pull-up)
Px.5, Px.6	complementary output	0
Px.7	complementary output	1

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.

LDB Px_DIR,#00011111B

LDB Px_MODE,#00000000B

LDB Px_REG,#10010011B

7-8