TCA6408_09 Datasheet, PDF (8/31 Pages) Texas Instruments – LOW-VOLTAGE 8-BIT I2C AND SMBus I/O EXPANDER WITH INTERRUPT OUTPUT, RESET, AND CONFIGURATION REGISTERS

TCA6408
LOW-VOLTAGE 8-BIT I²C AND SMBus I/O EXPANDER
WITH INTERRUPT OUTPUT, RESET, AND CONFIGURATION REGISTERS
SCPS151C – FEBRUARY 2007 – REVISED JUNE 2007
Interface Definition
BYTE
BIT
7 (MSB)
6
5
4
3
2
I²C slave address
L
H
L
L
L
L
I/O data bus
P7
P6
P5
P4
P3
P2
Device Address
The address of the TCA6408 is shown in Figure 4.
Slave Address
01
0
0
0
0
AD
DR
R/W
Fixed
Programmable
Figure 4. TCA6408 Address
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1
ADDR
P1
0 (LSB)
R/W
P0
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 TCA6408. 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
B7 B6
0
0
0
0
0
0
0
0
(1) Undefined
CONTROL REGISTER BITS
B5 B4 B3 B2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Command Byte
B1 B0
0
0
0
1
1
0
1
1
COMMAND
BYTE
(HEX)
00
01
02
03
REGISTER
Input Port
Output Port
Polarity Inversion
Configuration
PROTOCOL
Read byte
Read/write byte
Read/write byte
Read/write byte
POWER-UP
DEFAULT
xxxx xxxx⁽¹⁾
1111 1111
0000 0000
1111 1111
8
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