PC87413 datasheet(136/257 Pages) NSC

136 / 257 page

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

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136

Revision1.2

7.2

BASIC FUNCTIONALITY

The basic functionality of each GPIO pin is based on four configuration bits and a bit slice of runtime registers GPDO and

GPDI. The configuration and operation of a single pin GPIOXn (pin ‘n’ in port ‘X’) is shown in Figure 36.

Figure 36. GPIO Basic Functionality

7.2.1

Configuration Options

The GPCFG1 register controls the following basic configuration options:

• Port Direction - Controlled by the Output Enable bit (bit 0).

• Output Type - Push-pull vs. open-drain. It is controlled by Output Buffer Type (bit 1) by enabling/disabling the upper tran-

sistor of the output buffer.

• Static Pull-Up - May be added to any type of port (input, open-drain or push-pull). It is controlled by Pull-Up Control (bit 2).

• Pin Lock - GPIO pin may be locked to prevent any changes in the output value and/or the output configuration. The lock

is controlled by bit 3. It disables writes to the GPDO register bits, to bits 0-3 of the GPCFG1 register (including the Lock

bit itself) and to bits 4-6 of the GPCFG2 register. Once locked, it can be released by reset or by the UNLOCKG bit in the

ACBLKCTL register (see Section 6.3.4 on page 128 - PC87413 and PC87417).

The GPCFG2 register controls the following basic configuration options:

• Load Protection - Disables the Output Buffer (if enabled), the Static Pull-Up (if enabled) and the Input Buffer (if the Port

is not a GPO type) if the specific GPIO pin is connected to a VDD-powered device and the VDD power is not present

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

Data Out

Data In

Output

Enable

Output

Lock

Type

Static

Pull-Up

Enable

Push-Pull =1

Pull-Up

Control

Read Only

Read/Write

(Bit 3)

(Bit 2)

(Bit 1)

(Bit 0)

Lock

GPIO Pin Conﬁguration Registers 1 and 2

(GPCFG1)

ACCESS.bus

LPC Bus

VDD-powered

Load

Bus

Control

(Bits 6,5)

(Bit 4)

Lock

No_Vdd

(GPCFG2)

(GPDI)

(GPDO)

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