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MBD975

S

0

1

0

0

A2

A1

A0

1

A

start condition

DATA 1

R/W

acknowledge

from slave

A

DATA 4

1

SDA

READ FROM

PORT

t ph

DATA INTO

PORT

slave address (PCF8574)

data from port

data from port

acknowledge

from slave

stop

condition

t ps

DATA 4

P

DATA 2

DATA 3

t ir

t ir

t iv

INT

Fig.12 READ mode (input).

A LOW-to-HIGH transition of SDA, while SCL is HIGH is defined as the stop condition (P). Transfer of data can be stopped at any moment by a stop condition. When this occurs, data present

at the last acknowledge phase is valid (output mode). Input data is lost.