Philips Semiconductors
Octal SMBus Registered Interface
Product specification
PCA9556
SMBus Address
slave address
0 0 1 1 A2 A1 A0 R/W
fixed
programmable
su01048
Figure 5. PCA9556 address
SMBus Transactions
Data is transmitted to the PCA9556 registers using Write Byte transfers (see Figures 6 and 7). Data is read from the PCA9556 registers using
Read and Receive Byte transfers (see FIgures 8 and 9).
1 2345 6 78 9
SCL
slave address
command byte
data to port
SDA S 0 0 1 1 A2 A1 A0 0 A 0 0 0 0 0 0 0 1 A
start condition
WRITE TO
PORT
R/W acknowledge
from slave
acknowledge
from slave
DATA 1
DATA OUT
FROM PORT
Figure 6. WRITE to output port register via Write Byte Protocol
A
acknowledge
from slave
DATA 1 VALID
tpv
su01049
1 2345 6 78 9
SCL
slave address
command byte
data to register
SDA S 0 0 1 1 A2 A1 A0 0 A 0 0 0 0 0 0 1 1/0 A
start condition
R/W acknowledge
from slave
acknowledge
from slave
DATA
A
acknowledge
from slave
Figure 7. WRITE to I/O configuration or polarity inversion registers via Write Byte Protocol
su01050
1998 Dec 18
6