TCA6408A Datasheet, PDF (8/35 Pages) Texas Instruments – LOW-VOLTAGE 8-BIT I2C AND SMBus I/O EXPANDER WITH INTERRUPT OUTPUT, RESET, AND CONFIGURATION REGISTERS

TCA6408A
SCPS192C – APRIL 2009– REVISED JULY 2009............................................................................................................................................................. www.ti.com
BYTE
I²C slave address
I/O data bus
7 (MSB)
L
P7
Interface Definition
BIT
6
5
4
3
H
L
L
L
P6
P5
P4
P3
2
1
0 (LSB)
L
ADDR
R/W
P2
P1
P0
Device Address
The address of the TCA6408A is shown in Figure 4.
Slave Address
01
0
0
0
0
AD
DR
R/W
Fixed
Programmable
Figure 4. TCA6408A Address
ADDR
L
H
Address Reference
I²C BUS SLAVE ADDRESS
32 (decimal), 20 (hexadecimal)
33 (decimal), 21 (hexadecimal)
The last bit of the slave address defines the operation (read or write) to be performed. A high (1) selects a read
operation, while a low (0) selects a write operation.
Control Register and Command Byte
Following the successful acknowledgement of the address byte, the bus master sends a command byte, which is
stored in the Control Register in the TCA6408A. Two bits of this data byte state the operation (read or write) and
the internal registers (Input, Output, Polarity Inversion, or Configuration) that will be affected. This register can be
written or read through the I²C bus. The command byte is sent only during a write transmission.
B7 B6 B5 B4 B3 B2 B1 B0
Figure 5. Control Register Bits
Command Byte
CONTROL REGISTER BITS
B7 B6 B5 B4 B3 B2 B1 B0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
1
COMMAND
BYTE
(HEX)
00
01
02
03
REGISTER
PROTOCOL
POWER-UP
DEFAULT
Input Port
Output Port
Polarity Inversion
Configuration
Read byte
Read/write byte
Read/write byte
Read/write byte
xxxx xxxx
1111 1111
0000 0000
1111 1111
8
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