4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and

28-Port I/O Expander

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13

Table 4. 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

XXX

XX

XX

0

Configuration

Register

Shutdown Enabled

Transition Detection Disabled

0x04

00

X

X

XX

X

0

Input Mask

Register

All Clear (Masked Off)

0x06

X0

0

0

00

0

0

Port

Configuration

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

0x09

101

01

01

0

Port

Configuration

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

0x0A

101

01

01

0

Port

Configuration

P15, P14, P13, P12: GPIO Inputs Without

Pullup

0x0B

101

01

01

0

Port

Configuration

P19, P18, P17, P16: GPIO Inputs Without

Pullup

0x0C

101

01

01

0

Port

Configuration

P23, P22, P21, P20: GPIO Inputs Without

Pullup

0x0D

101

01

01

0

Port

Configuration

P27, P26, P25, P24: GPIO Inputs Without

Pullup

0x0E

101

01

01

0

Port

Configuration

P31, P30, P29, P28: GPIO Inputs Without

Pullup

0x0F

101

01

01

0

X = Unused bits; if read, zero results.

Table 5. Configuration Register Format

REGISTER DATA

FUNCTION

ADDRESS CODE

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

Configuration Register

0x04

M

0

XXXXXS

Table 6. Shutdown Control (S Data Bit D0) Format

REGISTER DATA

FUNCTION

ADDRESS CODE

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

Shutdown

0x04

M

0

XXXXX

0

Normal Operation

0x04

M

0

XXXXX

1