PCA9538 データシートの表示（PDF） - NXP Semiconductors.

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PCA9538

8-bit I2C-bus and SMBus low power I/O port with interrupt and reset

NXP Semiconductors. 

NXP Semiconductors

PCA9538

8-bit I2C-bus and SMBus low power I/O port with interrupt and reset

6.2.5 Register 3 - Configuration register

This register configures the directions of the I/O pins. If a bit in this register is set, the

corresponding port pin is enabled as an input with high-impedance output driver. If a bit in

this register is cleared, the corresponding port pin is enabled as an output. At reset, the

I/Os are configured as inputs.

Table 7. Register 3 - Configuration register bit description

Legend: * default value.

Bit Symbol Access Value Description

7

C7

R/W

1*

configures the directions of the I/O pins

6

C6

5

C5

4

C4

R/W

1*

R/W

1*

R/W

1*

0 = corresponding port pin enabled as an output

1 = corresponding port pin configured as an input

(default value)

3

C3

R/W

1*

2

C2

R/W

1*

1

C1

R/W

1*

0

C0

R/W

1*

6.3 Power-on reset

When power is applied to VDD, an internal Power-On Reset (POR) holds the PCA9538 in

a reset condition until VDD has reached VPOR. At that point, the reset condition is released

and the PCA9538 registers and state machine will initialize to their default states.

Thereafter, VDD must be lowered below 0.2 V to reset the device.

For a power reset cycle, VDD must be lowered below 0.2 V and then restored to the

operating voltage.

6.4 RESET input

A reset can be accomplished by holding the RESET pin LOW for a minimum of tw(rst).

The PCA9538 registers and SMBus/I2C-bus state machine will be held in their default

state until the RESET input is once again HIGH. This input requires a pull-up resistor to

VDD if no active connection is used.

6.5 Interrupt output

The open-drain interrupt output (INT) is activated when one of the port pins changes state

and the pin is configured as an input. The interrupt is de-activated when the input returns

to its previous state or the Input Port register is read.

Note that changing an I/O from an output to an input may cause a false interrupt to occur

if the state of the pin does not match the contents of the Input Port register.

PCA9538_5

Product data sheet

Rev. 05 — 28 May 2009

© NXP B.V. 2009. All rights reserved.

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