Data Sheet

1997 Apr 02 10
Philips Semiconductors Product specification
Remote 8-bit I/O expander for I
2
C-bus
PCF8574
handbook, full pagewidth
MBD975
S 0 1 0 0 A2 A1 A0 1 A
start condition
DATA 1
R/W acknowledge
from slave
A
DATA 4
1SDA
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.11 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.