USB MultiSwitchTM Hub

Datasheet

7.3.7Bus Reset Sequence

The SMBus Slave Interface resets and returns to the idle state upon a START field followed immediately by a STOP field.

7.3.8SMBus Alert Response Address

The SMBALERT# signal is not supported by the Hub.

7.3.8.1Undefined Registers

Reads to undefined registers return 00h. Writes to undefined registers have no effect and do not return an error.

7.3.8.2Reserved Registers

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

7.4Default Strapping Option

The USB2524 can be configured via a combination of internal default values and pin strap options.

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.

The LED_A[4:1]_N 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 in Figure 7.3, "LED Strapping Option" shows a recommended passive scheme. When a pin is configured with a “Strap High” configuration, the LED functions with active low signaling, 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 signaling, and the PAD will source the current to the external LED.

+V

Strap High

 

100K

LED

LED

Pin

 

HUB

LED

 

Pin

Strap Low

 

100K

 

LED

Figure 7.3 LED Strapping Option

7.5Default Configuration

When configured for Internal Defaults only, the Default ROM values in Table 7.1, "Internal EEPROM & SMBus Register Memory Map" lists the values which will be used to configure the various hub features.

SMSC USB2524

43

Revision 1.91 (08-22-07)

 

DATASHEET