Datasheet

1000 0001, 0x02, 0x02, 0x02, …

Command byte:

B7 = 1 enables auto-increment mode

B6 = 0

B5 = 0

B4-B0 = 0 0001 points to Device ID and Control register

Data byte write to

Device ID and Control Register

Data byte write to

I/O Direction Register

Data byte write to

Output State Register

TCA7408

SCPS235B –NOVEMBER 2011–REVISED MARCH 2013

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DEVICE ADDRESS

The address of the device is shown below

ADDRESS REFERENCE

SLAVE ADDRESS

ADDR I

C BUS SLAVE ADDRESS

B7 B6 B5 B4 B3 B2 B1 B0

0 1 0 0 0 0 1 1 0 (W) 134 (decimal), 86(h)

0 1 0 0 0 0 1 1 1 (R) 135 (decimal), 87(h)

1 1 0 0 0 1 0 0 0 (W) 136 (decimal), 88(h)

1 1 0 0 0 1 0 0 1 (R) 137 (decimal), 89(h)

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 TCA7408. Five bits of this data byte state the operation (read or write) and

the internal registers that will be affected. This register can be written or read through the I

C bus. The command

byte is sent only during a write transmission.

AUTO INCREMENT MODE

An automatic increment feature as been added to the control register for block writes. The master can write to all

10 registers with 1 command byte being sent initially. In auto-increment mode the last five bits of the command

byte are automatically incremented after the byte is written and the next data byte is stored in the corresponding

registers do not change the value in the register.

If B7=0, all the data bytes are written to or read from the register defined by B4 through B0 in a non-incremented

fashion. B6 and B5 should always be 0.

Product Folder Links :TCA7408