PCA8575_2

© NXP B.V. 2007. All rights reserved.

Product data sheet

Rev. 02 — 21 March 2007

8 of 30

NXP Semiconductors

PCA8575

8.3 Reading from a port (Input mode)

All ports programmed as input should be set to logic 1. To read, the master

(microcontroller) first addresses the slave device after it receives the interrupt. By setting

the last bit of the byte containing the slave address to logic 1 the Read mode is entered.

The data bytes that follow on the SDA are the values on the ports.

If the data on the input port changes faster than the master can read, this data may be

lost.

Fig 11. Write mode (output)

A5 A4 A3 A2 A1 A0

0

A

SA6

slave address

START condition

R/W

acknowledge

from slave

002aab632

P

06

1

P

07

data to port 0

A

acknowledge

from slave

12345678

SCL

9

SDA

A

acknowledge

from slave

write to port

data output from port

P05

data to port 1

data A0 and B0 valid

P16 output voltage

P16 pull-up output current

INT

P

04

P

03

P

02

P

01

P

00

P

17

P

14

P

13

P

12

P

11

P

10

1

P16

P

15

data A0 and B0 valid

P05 output voltage

P05 pull-up output current