4-Port USB 2.0 Controller

Datasheet

SMSC USB20H04

Page 17

Revision 1.63 (03-30-07)

DATASHEET

7.5

Serial Interface

External configuration data is loaded via the serial interface. The serial interface appears as either an

SMBus slave, or an I

7.5.1

SMBus Slave

The USB20H04 conforms to voltage, power, and timing specifications as set forth in the SMBus 1.0

Specification for Slave-Only devices. The SMBus interface shares the same pins as the EEPROM

interface. If the SMB_SEL_N pin is configured to activate the SMBus interface, external EEPROM support

is no longer available and the user-defined configuration values must be downloaded via the SMBus. A

separate Application Note 9.29, "USB20H04 4-Port USB 2.0 Hub Controller - Configuration Programming"

provides details for configuring the USB20H04 via the SMBus.

7.5.2

I

A basic I

reset. The USB20H04 acts as the master and generates the serial clock and the START and STOP

conditions.

7.6

Repeater

The hub repeater is responsible for managing connectivity between upstream and downstream facing ports

which are operating at the same speed. The repeater includes both a high-speed repeater function and a

full-/low-speed repeater function. When the upstream port is operating in a high-speed environment, traffic

passes through the high-speed repeater to downstream ports that are operating at high-speed. As detailed

in the USB specification, the repeater is responsible for managing connectivity on a ‘per packet’ basis. It

implements ‘packet signaling’ and ‘resume’ connectivity. If a low-speed device is detected the repeater will

not propagate upstream packets to the corresponding port, unless they are preceded by a PREAMBLE

PID.

7.7

SIE

Communication with the host is handled by the SIE. The full USB protocol layer is implemented in the SIE,

including Endpoint 0 and Endpoint 1. All standard USB requests from the host are handled by the

hardware without the need for firmware intervention.

7.8

Controller

The controller implements protocol handling at a higher level. By responding to SETUP packets it

coordinates enumeration, and it manages suspend/resume operation.