Philips Semiconductors
Product data
Octal SMBus and I
2
C registered interface
PCA9556
SMBus Address
slave address
0
0
1
1
A2
A1
A0 R/W
fixed
programmable
su01048
Figure 6. PCA9556 address
SMBus Transactions
Data is transmitted to the PCA9556 registers using Write Byte transfers (see Figures 7 and 8). Data is read from the PCA9556 registers using
Read and Receive Byte transfers (see FIgures 9 and 10).
SCL
1
2
3
4
5
6
7
8
9
command byte
slave address
data to port
SDA
S
0
0
1
1
A2
A1
A0
0
R/W
A
0
0
0
0
0
0
0
1
A
acknowledge
from slave
DATA 1
A
P
start condition
acknowledge
from slave
acknowledge
from slave
WRITE TO
PORT
DATA OUT
FROM PORT
t
pv
DATA 1 VALID
SW00797
Figure 7. WRITE to output port register via Write Byte Protocol
SCL
1
2
3
4
5
6
7
8
9
slave address
command byte
data to register
SDA
S
0
0
1
1
A2
A1
A0
0
R/W
A
0
0
0
0
0
0
1
1/0
A
acknowledge
from slave
DATA
A
P
start condition
acknowledge
from slave
acknowledge
from slave
SW00798
Figure 8. WRITE to I/O configuration or polarity inversion registers via Write Byte Protocol
2002 Mar 28
7
PHILIPS [ NXP SEMICONDUCTORS ]
