USB97C102 datasheet(67/80 Pages) SMSC

67 / 80 page

SMSC DS – USB97C102

Page 67

Rev. 03/23/2000

HUB BYPASS MODE

Hub Bypass mode is a configuration option availaible to the SMSC USB978C102. This optional mode of operation

allows the system developer the ability to disconnect the Internal USB 1.1 compliant Hub from the SIE. The reasons

why a designer would want ot do this is as follows:

The designer may want to disconnect the USB Hub from the USB function for diagnostic purposes.

This option give the designer the ability to make the USB 97C102 backward compatible to the SMSC USB

97C100 device.

Disconnecting the USB Hub from the USB function

In “HubBypass mode”, see Table 118 – Hub Control Register1 on page 65, setting the appropriate bit HubBypass2,

HubBypass3, etc., will connect the associated Hub Down stream port to the internal SIE function.

Please note that only one HubBypass bit should be set at one time. Setting more than one bit will cause

unexpected results.

USB97C100 Compatibility Mode

The SMSC USB97C102 can be placed in a mode to emulate the SMSC USB97C100 in terms of functionality. The

SMSC USB97C102 can also be “Pin” compatible to the USB97C100. Please refer to the application note titled

“Utilizing the SMSC USB97C102 in USB97C100 designs” for additional information.

In order to place the USB97C102 in a mode that is pin and function compatible to the SMSC USB97C100, the SMSC

USB97C102 should have the “HubBypass2” bit set in the HubControl1 register. See Table 118 – Hub Control

Register1 on page 65.

The diagram shown in FIGURE 8 shows the Hub configured for hub bypass mode 2.

FIGURE 8 – HUBBYPASS2

USB Hub Block

PORT0

PORT1

Internal

SIE

PORT2

Upstream Port

for Port 1

Upstream Port

Down Stream Ports

PORT3 PORT4 PORT5

USB97C102 датащи(PDF) 67 Page - SMSC Corporation