USB97C102 Datasheet, PDF (67/80 Pages) SMSC Corporation – Multi-Endpoint USB Peripheral Controller with Integrated 5 Port HUB

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:
1) The designer may want to disconnect the USB Hub from the USB function for diagnostic purposes.
2) 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.
PORT0
Upstream Port
USB Hub Block
X
Down Stream Ports
PORT1
To
Internal
SIE
X
Upstream Port
for Port 1
PORT2
FIGURE 8 – HUBBYPASS2
PORT3 PORT4 PORT5
SMSC DS – USB97C102
Page 67
Rev. 03/23/2000