SMSC USB2502 User Manual

2-Port USB 2.0 Hub Controller

Revision 2.3 (08-27-07)

32

SMSC USB2502

Unless otherwise instructed, only a ‘0’ may be written to all reserved registers or bits.

The SMSC Hub can be configured via its internal default configuration. (please see  for specific details
on how to enable default configuration. 

Please refer to 

 for the internal default values that are loaded when this option is

selected.

The SMSC Hub can be configured via a combination of internal default values and pin strap options.
Please see 

 for specific details on how to enable the

default/pin-strap configuration option. 

The strapping option pins only cover a limited sub-set of the configuration options. The internal default
values will be used for the bits & registers that are not controlled by a strapping option pin. Please
refer to 

 for the internal default values that are loaded when this option is selected. 

The Green LED pins are sampled after RESET_N negation, and the logic values are used to configure
the hub if the internal default configuration mode is selected. The implementation shown below (see

) shows a recommended passive scheme. When a pin is configured with a “Strap High”

configuration, the LED functions with active low signalling, and the PAD will “sink” the current from the
external supply. When a pin is configured with a “Strap Low” configuration, the LED functions with
active high signalling, and the PAD will “source” the current to the external LED. 

There are two different resets that the Hub experiences. One is a hardware reset (via the RESET_N
pin) and the second is a USB Bus Reset.

HUB

50K

Strap Low

GR2

50K

Strap High

GR1

+V