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8574A

Remote 8-bit I/O expander for I2C-BUS

Philips Electronics 

Philips Semiconductors

Remote 8-bit I/O expander for I2C-bus

7 FUNCTIONAL DESCRIPTION

Product specification

PCF8574

handbook, full pagewidth

write pulse

data from

shift register

power-on

reset

read pulse

data to

shift register

DQ

FF

CI

S

DQ

FF

CI

S

VDD

100

µA

P0 to P7

V SS

to interrupt

logic

MBD977

Fig.9 Simplified schematic diagram of each I/O.

7.1 Addressing

For addressing see Figs 10, 11 and 12.

handbook, full pagewidth

slave address

S 0 1 0 0 A2 A1 A0 0 A

a. PCF8574.

slave address

S 0 1 1 1 A2 A1 A0 0 A

MBD973

b. PCF8574A.

Fig.10 PCF8574 and PCF8574A slave addresses.

Each of the PCF8574’s eight I/Os can be independently used as an input or output. Input data is transferred from the

port to the microcontroller by the READ mode (see Fig.12). Output data is transmitted to the port by the WRITE mode

(see Fig.11).

2002 Nov 22

9

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