CS5535 datasheet(149/555 Pages) NSC

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GPIO Subsystem Functional Description (Continued)

4.15.4 GPIO Basic I/O Configuration

The General Purpose Input and Output (GPIO) Interface is

illustrated in Figure 4-49. The figure represents one of

twenty-eight GPIOs potentially available. Note the GPIOs

[31:29] and [23] are non-existent. Table 2-8 "GPIO

Options" on page 42 provides a complete list of features for

each GPIO and should be consulted when configuring a

system.

Each GPIO has basic configuration options used to set up

the characteristics of the GPIO for either input or output.

Each of the functions in the list below follows the GPIO reg-

ister strategy outlined inSection 4.15.2 "Register Strategy"

on page 148 unless otherwise noted. This strategy allows

individual GPIOs to be modified without accidentally

changing the characteristics of unrelated GPIOs, and with-

out requiring ‘read-modify-write’ cycles. All values are

active high.

• OUT_EN. When high, enables this GPIO for output. A

pad may be configured for output, input, or both.

• IN_EN. Enables this GPIO for input. A pad may be

configured for input, output, or both.

• OUT_VAL. This will establish the value driven to the pad

when it is selected as an Output, unless either

OUT_AUX1 or OUT_AUX2 are selected. The value

driven to the GPIO pad is subject to an optional inver-

sion.

• OUT_INVRT_EN. When high, inverts the Output Value.

• IN_INVRT_EN. Inverts the signal applied to the ball, and

presents the inverted value to all follow-up circuitry (i.e.,

input conditioning functions).

• OUT_OD_EN. Configures this GPIO for open-drain

operation. When the output pad is to be driven low, the

pad is driven low. When the output pad is to be driven

high, the pad is allowed to float and is not driven.

• OUT_AUX1_SEL and OUT_AUX2_SEL. Selects an

internal auxiliary source for the Output Value. Table 2-8

"GPIO Options" on page 42 identifies all the possible

internal connections for these two auxiliary sources.

• IN_AUX1_SEL. Selects an internal source as an input

instead of the ball. Table 2-8 "GPIO Options" on page 42

lists all the functions that may be connected in this

manner.

• PU_EN. Applies a weak pull-up to the pad. The effect of

this control is independent of all other settings except

PD_EN. If PU_EN is set by software, PD_EN is auto-

matically cleared.

• PD_EN. Applies a weak pull-down to the pad. The effect

of this control is independent of all other settings except

PU_EN. If PD_EN is set by software, PU_EN is auto-

matically cleared.

Figure 4-49. GPIO Configuration

Event

Counter

Digital

Filter

Ball

Pull-Down

Enable

Open-Drain

Enable

Output

Enable

Output Invert

Enable

Read

Status

[7:0]

Input

Invert

Input

Enable

Pull-Up

Enable

Positive

Edge

Enable

Event

Count

Event Count

Enable

Filter

Amount

Filter

Enable

Input Conditioning Functions

(1 of 8)

AUX1

AUX2

Negative Edge

Enable

PME

Interrupts

Event Enable

X,Y,Z,W Interrupt Mapping Registers

X,Y,Z,W PME Mapping Registers

Output

Value

Enable

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