2-Port USB 2.0 Hub Controller

Datasheet

5.3.9.19Reserved Registers

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

5.4Default Configuration Option:

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 Table 5.1 on page 19 for the internal default values that are loaded when this option is selected.

5.5Default Strapping Options:

The SMSC Hub can be configured via a combination of internal default values and pin strap options. Please see Table 4.1, "7-Port Hub Pin Descriptions" 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 Table 5.1 on page 19 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 Figure 5.1) 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.

+V

Strap High

50K

GR1

HUB

GR2

Strap Low

50K

Figure 5.1 LED Strapping Option

5.6Reset

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.

Revision 2.3 (08-27-07)

32

SMSC USB2502

 

DATASHEET