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DS20006363D-page 25

SY75608/612

5.2.1

I2C BUS READ/WRITE

Reading or writing a register or registers in a I2C Bus client device is MSB first and LBS last in one-byte blocks.

The access from I2C server starts with the start condition followed by the client address and the write indicator bit. This

is then followed by the command byte which in bits [6:0] contains the address of the register to be accessed for byte

mode or the first register to be accessed in the burst mode. The most significant bit in the command byte must be set

to 1.

Byte Read. The standard byte read is as shown in Figure 5-4. The command byte is followed the client address and

read indication bit. The device (client) will respond by sending the requested byte.

FIGURE 5-4:

I2C Bus Byte Read.

Write. Figure 5-5 illustrates the standard byte write. After the written byte has been acknowledged by the device, the

server will assert the stop signal.

FIGURE 5-5:

I2C Bus Byte Write.

T

Slave

Command

r

Slave

A

N

P

Wr

Rd

Start

Condi on

Rd/Wr Command

Register address to read

MSB = 1

{1'b1,register_address[6:0]}

Repeat start

Acknowledge

Not Ack

Stop

Condi on

Master

drives Bus

Slave

drives Bus

A

A

Data Byte 0

Byte

Byte

Byte

Byte

Rd/Wr Command

T

Slave

Command

P

Wr

Start

Condi on

Register address to write

MSB = 1

{1'b1,register_address[6:0]}

Acknowledge

Stop

Master

drives Bus

Slave

drives Bus

A

Data Byte 0

A

A

Byte

Byte

Byte

Rd/Wr Command