Specifications

47
3706C–MICRO–2/11
AT89LP3240/6440
Figure 10-3. Input Circuit for P3.2, P3.3, P4.0, P4.1 and P4.2
10.1.3 Open-drain Output
The open-drain output configuration turns off all pull-ups and only drives the pull-down transistor
of the port pin when the port latch contains a logic “0”. To be used as a logic output, a port con-
figured in this manner must have an external pull-up, typically a resistor tied to V
DD
. The pull-
down for this mode is the same as for the quasi-bidirectional mode. The open-drain port configu-
ration is shown in Figure 10-4. The input circuitry of P3.2, P3.3, P4.0, P4.1 and P4.2 is not
disabled during Power-down (see Figure 10-3) and therefore these pins should not be left float-
ing during Power-down when configured in this mode.
Figure 10-4. Open-Drain Output
10.1.4 Push-pull Output
The push-pull output configuration has the same pull-down
structure as both the open-drain and
the quasi-bidirectional output modes, but provides a continuous strong pull-up when the port
latch contains a logic “1”. The push-pull mode may be used when more source current is needed
from a port output. The push-pull port configuration is shown in Figure 10-5.
Figure 10-5. Push-pull Outp
ut
Port
Pin
Input
Data
Port
Pin
From Port
Register
Input
Data
PWD
Port
Pin
V
CC
From Port
Register
Input
Data
PWD