USB2524 datasheet(43/57 Pages) SMSC

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USB MultiSwitchTM Hub

Datasheet

SMSC USB2524

Revision 1.91 (08-22-07)

DATASHEET

7.3.7

Bus Reset Sequence

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

immediately by a STOP field.

7.3.8

SMBus Alert Response Address

The SMBALERT# signal is not supported by the Hub.

7.3.8.1

Undefined Registers

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

an error.

7.3.8.2

Reserved Registers

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

7.4

Default 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.

Figure 7.3 LED Strapping Option

7.5

Default 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.

HUB

100K

Strap Low

LED

100K

Strap High

LED

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