pc87591l-n05 National Semiconductor Corporation, pc87591l-n05 Datasheet - Page 111

• Manufacturer Part Number: pc87591l-n05
• Description: Lpc Mobile Embedded Controller
• Manufacturer: National Semiconductor Corporation

Revision 1.2
4.0 Embedded Controller Modules
4.5.2
Bidirectional Port with Alternate Function
The GPIO port enables access to input and output pins. It also controls the pin usage either as an I/O port or in its alternate
function. Figure 32 shows this functionality.
Output Buffer
The output buffer is a TRI-STATE buffer. The output type (i.e., CMOS or TTL) and its driving capabilities are described in
Section 2.2 on page 38.
Input Buffer
The I/O port input buffer characteristics are defined in Section 2.2 on page 38.
The input buffer has an enable input. When enabled, the buffer inputs the pin’s logic level to the on-chip modules. When
disabled, the input is blocked to prevent supply leakage currents.
Weak Pull-Up
The weak pull-up is enabled when the corresponding bit of PxWPU is set (1) and the pin is configured as an input port. When
the pin is configured for input, this pull-up can prevent the input from being in an undefined state. When the pin is configured
as an output port, this pull-up is disabled.
• General-Purpose Input/Output (GPIO) Port (Pw).
• Each I/O pin can be configured as a GPIO port or as an alternate function.
— DEV environment support.
— Each pin functions as input or output signal.
— Direction register controls the port direction.
— Read-back on all registers.
— Some I/O or input pins can provide interrupt functions.
— Pins shared with DEV environment signals.
— Off-chip implementation supported in DEV environments.
— Binary and cycle-by-cycle compatibility between environments.
GPIO Port Px
Weak Pull-Up
Register
Alt Device Direction
Direction
Register
Alt Device Data
Output
Data Output
Register
Data Input Register
Alt Device Data Input
Data Input Read
Alternate
Function
Register
{
{
{
{
Figure 32. GPIO Port Px Schematic Diagram
PxDIN
Weak Pull-Up
(Continued)
(PxDOUT)
(PxWPU)
Data Out
Direction
(PxDIR)
PxAlt
111
Alt
Alt
Alt
Alt
Pull-Up
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