6-11

I/O PORTS
6.3.3 Bidirectional Port Pin Configurati on ExampleAssume that you wish to configure the pins of a bidirectional port as shown in Table 6-9.To do so, you could use the following e xample code segment. Table 6-10 shows t he state of eachpin after reset and after execution of each line of the example code.
LDB P
x
_DIR,#00011111B
LDB P
x
_MODE,#00000000B
LDB P
x
_REG,#10010011B

Table 6-8. Control Register Values for Each Configuration

Desired Pin Configuration Configuration Register S ettings
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, stron gly driving 0 1 0 0
Open-drain output, high impedance 1 0 1
Input 1 0 1
Special-function sign al P
x
_DIR P
x
_MODE†P
x
_REG
Complementa ry output, output value controlle d by periphera l 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 hig h.

Table 6-9. 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-dra in ou tp ut 0
P
x
.4 open-drain outp ut 1 (assuming externa l pull-up)
P
x
.5, P
x
.6 complementary o utput 0
P
x
.7 compleme ntary output 1