PC87372 datasheet(65/144 Pages) NSC

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5.0 General-Purpose Input/Output (GPIO) Ports (Continued)

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Revision 1.2

The GPCFG2 register controls the Load Protection configuration option:

• V

DD-Powered Load: Disables the Output Buffer (if enabled), the Static Pull-Up (if enabled) and the Input Buffer if the

specific GPIO pin is connected to a VDD-powered device and VDD3 power to the PC87372 is not present (No_Vdd). This

function is controlled by the VDD-powered Load bit (bit 4).

5.2.2

Operation

If the output is enabled, the value that is written to the GPDO or GPDIO registers is driven to the pin. Reading from the GPDO

The GPDI register is a read-only register. Reading from the GPDI register returns the actual pin value regardless of its

source (the port itself or an external device). Writing to this register is ignored.

Reading from the GPDIO register returns the actual pin value regardless of its source.

Activation of the GPIO module is controlled by device-specific configuration bits. When this module is inactive, access

through the LPC bus to the runtime registers (GPDI, GPDO and GPDIO) is disabled; however, there is no change in the

GPDO and GPDIO values and therefore there is no effect on the outputs of the pins.

The configuration and data registers of each GPIO pin are reset according to the setting of VDDLOAD bit in GPCFG2 reg-

ister (see Section 3.13.6 on page 59).

5.3 EVENT HANDLING AND SYSTEM NOTIFICATION

The enhanced GPIO port (GPIOE) supports system notification based on event detection. This functionality is based on

configuration bits and a bit slice of runtime registers GPEVEN and GPEVST. The configuration and operation of the event

detection capability is shown in Figure 11. System notification is described in Section 5.3.2.

Figure 11. Event Detection

5.3.1

Event Configuration

Each pin in the GPIO port is a potential input event source. The event detection can trigger a system notification upon prede-

termined behavior of the source pin. The GPCFG1 register determines the event detection trigger type for system notification.

Event Debounce Enable

The input signal can be debounced for at least 16 ms, before entering the detector. To ensure that the signal is stable, the

signal state is transferred to the event detector only after a debouncing period during which the signal has no transitions.

The debouncer adds a delay equal to the debouncing period to both assertion and de-assertion of the event pending indi-

cator (IRQ, SCI). The debounce is controlled by Event Debounce Enable (bit 6 of GPCFG1 register).

Event

Enable

Event Polarity

Input

Debouncer

Event

Internal

Bus

Level =1

Write 1 to Clear

Status

Rising Edge or

Rising

Edge

Detector

High Level =1

GPIO Pin Conﬁguration Register 1

Event Type

Event

Debounce

Enable

R/W

Bit 6

Bit 5

Bit 4

Indication

Pending

(GPCFG1)

Reset

Set

GPIO Event Indication to SWC

Read

GPIO

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