USB5534B Datasheet, PDF (30/73 Pages) Microchip Technology – 4-Port SS/HS USB Hub Controller

USB5534B
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
Denotes Master-to-Slave
Denotes Slave-to-Master
1
7
11
16
1
S
Slave Address
Wr A SMBus RAM Buffer Offset A _...
8
1
8
1
8
1
Byte Count = N A Data byte 1 A Data byte 2 A
8
11
Data byte N A P
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
1
7
11
S Slave Address Wr A
16
SMBus RAM
Buffer Offset
11
7
11
A S Slave Address Rd A _...
8
1
8
1
8
1
Byte Count = N A Data byte 1 A Data byte 2 A
8
11
Data byte N A P
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
1
7
11
S
Slave Address
Wr A
16
OPCODE
1
A _...
DS00001681C-page 30
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