Datasheet

0 1 0 0 A1A2 A0
Slave Address
R/W
Fixed
Hardware
Selectable
0 0 0 0 B1 B000
PCA9534
www.ti.com SCPS124G –SEPTEMBER 2006–REVISED JUNE 2010
Table 3. Interface Definition
BIT
BYTE
7 (MSB) 6 5 4 3 2 1 0 (LSB)
I
2
C slave address L H L L A2 A1 A0 R/W
Px I/O data bus P7 P6 P5 P4 P3 P2 P1 P0
Device Address
Figure 4 shows the address byte of the PCA9534.
Figure 4. PCA9534 Address
Table 4. Address Reference
INPUTS
I
2
C BUS SLAVE ADDRESS
A2 A1 A0
L L L 32 (decimal), 20 (hexadecimal)
L L H 33 (decimal), 21 (hexadecimal)
L H L 34 (decimal), 22 (hexadecimal)
L H H 35 (decimal), 23 (hexadecimal)
H L L 36 (decimal), 24 (hexadecimal)
H L H 37 (decimal), 25 (hexadecimal)
H H L 38 (decimal), 26 (hexadecimal)
H H H 39 (decimal), 27 (hexadecimal)
The last bit of the slave address defines the operation (read or write) to be performed. When it is high (1), a read
is selected, while a low (0) selects a write operation.
Control Register and Command Byte
Following the successful acknowledgment of the address byte, the bus master sends a command byte, which is
stored in the control register in the PCA9534. Two bits of this command byte state the operation (read or write)
and the internal register (input, output, polarity inversion or configuration) that will be affected. This register can
be written or read through the I
2
C bus. The command byte is sent only during a write transmission.
Once a command byte has been sent, the register that was addressed continues to be accessed by reads until a
new command byte has been sent.
Figure 5. Control Register Bits
Table 5. Command Byte
CONTROL
COMMAND POWER-UP
REGISTER BITS
REGISTER PROTOCOL
BYTE (HEX) DEFAULT
B1 B0
0 0 0x00 Input Port Read byte xxxx xxxx
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