CS5376-BS View Datasheet(PDF) - Cirrus Logic

Part Name

Description

MFG CO.

CS5376-BS

Low Power Multi-Channel Decimation Filter

Cirrus Logic 

CS5376

CS output from SPI

Data bit

GP_PULL

GP_DATA

Pull Up

Logic

R

GPIO/CS

GP_DIR

Figure 58. GPIO Bi-directional Structure and Operation

14. GENERAL PURPOSE I/O PINS

The General Purpose I/O (GPIO) block provides 12

general purpose pins to interface with external

hardware. Each GPIO pin can be configured as an

input or an output, with an internal pull-up resistor

enabled or disabled. Several GPIO pins also double

as chip selects for the SPI 1 and SPI 2 ports. Fig-

ure 58 shows the structure of a bi-directional GPIO

pin with SPI chip select functionality.

Each GPIO pin is programmed by three bits in the

GPCFG0 or GPCFG1 registers. The input or output

data direction is selected by the GP_DIR bits, the

internal pull-ups are enabled or disabled by the

GP_PULL bits, and the data values are set by the

GP_DATA bits. After reset, the GPIO pins are de-

faulted as inputs with pull-up resistors enabled.

14.1 GPIO Input Mode

When reading a value from the GP_DATA bits, the

returned data reports the current state of the pins. If

a pin is externally driven high it reads a logical 1. It

also reads a logical 1 if the pin is not connected

with its pull-up resistor enabled. If a pin is external-

ly driven low it reads a logical 0. It also reads a log-

ical 0 if the pin is not connected with its pull-up

resistor disabled, due to leakage currents.

When a GPIO pin is used as an input, the pull-up

resistor should be disabled to save power if it isn’t

required.

14.2 GPIO Output Mode

When a GPIO pin is used as an output to an external

device, the reset configuration as an input with

pull-up resistors enabled results in a logic high out-

put to the external device until it is programmed.

When a GPIO pin is programmed as an output with

a data value of 0, the pin is driven low and the in-

ternal pull-up resistor is automatically disabled.

When programmed as an output with a data value

of 1, the pin is driven high and the pull-up resistor

is inconsequential.

Any GPIO pin can be used as an open-drain output

by setting the data value to 0, enabling the pull-up,

and using the GP_DIR direction bits to control the

pin value. This open-drain output configuration

uses the internal pull-up resistor to pull the pin high

when GP_DIR is set as an input, and drives the pin

low when GP_DIR is set as an output.

14.2.1 GPIO Read In Output Mode

Note that when read the GP_DATA value always

reports the current state of the pins, and a value

written in output mode does not necessarily read

back the same value. If a pin in output mode is writ-

ten as a logical 1, the CS5376 will drive the pin

high. If an external device then forces the pin low,

the read value will reflect the pin state and return a

logical 0. Similarly, if an output pin is written as a

logical 0 but forced high externally, the read value

will reflect the pin state and return a logical 1. In

DS256PP1

85

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