USB2422SLASHMJ datasheet(22/51 Pages) SMSC

22 / 51 page

2-Port USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 1.0 (06-04-13)

SMSC USB2422

DATASHEET

6. Complies with Section 11.10 of the USB 2.0 Specification for behavior after completion of the reset

sequence. The host then configures the hub and the hub’s downstream port devices in accordance

with the specification.

The hub does not propagate the upstream USB reset to downstream devices.

4.3

SMBus

The SMSC hub can be configured by an external processor via an SMBus interface (see Table 4.1 for

details on enabling the SMBus interface). The SMSC hub waits indefinitely for the SMBus code load

to complete and only appears as a newly connected device on USB after the code load is complete.

The hub’s SMBus acts as a slave-only SMBus device. The implementation only supports block write

(Section 4.3.2.1) and block read (Section 4.3.2.2) protocols. Reference the System Management Bus

Specification [2] for additional information.

Refer to Section 4.4, "SMBus Registers," on page 24 for details on all SMBus accessible registers.

4.3.1

SMBus Slave Address

The 7-bit slave address is 0101100b. The hub will not respond to the general call address of 0000000b.

4.3.2

Protocol Implementation

Typical block write and block read protocols are shown in figures 4.2 and 4.3. Register accesses are

performed using 7-bit slave addressing, an 8-bit register address field, and an 8-bit data field. The

shading shown in the figures during a read or write indicates the hub is driving data on the SMBDATA

line; otherwise, host data is on the SMBDATA line.

The SMBus slave address assigned to the hub (0101100b) allows it to be identified on the SMBus.

The register address field is the internal address of the register to be accessed. The register data field

is the data that the host is attempting to write to the register or the contents of the register that the

host is attempting to read.

Note: Data bytes are transferred MSB first.

4.3.2.1

Block Write/Read

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.

Note: For the following SMBus tables:

Figure 4.2 Block Write

4.3.2.2

Block Read

A block read differs from a block write in that the repeated start condition exists to satisfy the SMBus

specification’s requirement for a change in the transfer direction.

Denotes Master-to-Slave

Denotes Slave-to-Master

Slave Address

171

...

Byte Count = N

Data byte 1

Data byte 2

Data byte N

USB2422/MJ Datasheet(PDF) 22 Page - SMSC Corporation

USB2422/MJ Datasheet(HTML) 22 Page - SMSC Corporation

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