USB5533B datasheet(30/71 Pages) MICROCHIP

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USB5533B

DS00001680C-page 30

 2012 - 2015 Microchip Technology Inc.

5.5.1

BLOCK WRITE

The block write begins with a slave address and a write condition. After the command code, the host issues a byte count

which describes how many more bytes will follow in the message. If a slave had 20 bytes to send, the first byte would

be the number 20 (14h), followed by the 20 bytes of data. The byte count may not be zero. A block write or read allows

a transfer maximum of 32 data bytes.

For the following SMBus tables:

FIGURE 5-4:

BLOCK WRITE

5.5.2

BLOCK READ

A block read differs from a block write in that the repeated start condition exists to satisfy the I2C specification’s require-

ment for a change in the transfer direction.

FIGURE 5-5:

BLOCK READ

5.5.3

STANDARD SMBUS COMMANDS

There are special commands that can be sent in the place of the 16-bit address bytes. These commands are used to

enumerate the hub, access the configuration registers, or simply reset the device. The commands consist of the 16-bit

command followed by a 00h byte to terminate the command.

FIGURE 5-6:

SMBUS COMMANDS

Denotes Master-to-Slave

Denotes Slave-to-Master

Slave Address

SMBus RAM Buffer Offset

...

Byte Count = N

Data byte 1

Data byte 2

Data byte N

Slave Address

SMBus RAM

Buffer Offset

Slave Address

...

Byte Count = N

Data byte 2

Data byte 1

Data byte N

Slave Address

OPCODE

...

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