2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port I/O Expander

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15

Table 6. Power-Up Configuration

REGISTER DATA

REGISTER

FUNCTION

POWER-UP CONDITION

ADDRESS

CODE

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

Port Register

Bits 4 to 31

GPIO Output Low

0x24 to

0x3F

XX

XX

X

X

X

0

Configuration

Register

Shutdown Enabled

Transition Detection Disabled

0x04

0

0

X

X

X

X

X

0

Input Mask

Register

All Clear (Masked Off)

0x06

X

0

0

0

0

0

0

0

Port

Configuration

P7, P6, P5, P4: GPIO Inputs without Pullup

0x09

1

0

1

0

1

0

1

0

Port

Configuration

P11, P10, P9, P8: GPIO Inputs without Pullup

0x0A

1

0

1

0

1

0

1

0

Port

Configuration

P15, P14, P13, P12: GPIO Inputs without Pullup

0x0B

1

0

1

0

1

0

1

0

Port

Configuration

P19, P18, P17, P16: GPIO Inputs without Pullup

0x0C

1

0

1

0

1

0

1

0

Port

Configuration

P23, P22, P21, P20: GPIO Inputs without Pullup

0x0D

1

0

1

0

1

0

1

0

Port

Configuration

P27, P26, P25, P24: GPIO Inputs without Pullup

0x0E

1

0

1

0

1

0

1

0

Port

Configuration

P31, P30, P29, P28: GPIO Inputs without Pullup

0x0F

1

0

1

0

1

0

1

0

X = unused bits; if read, zero results.