SMSC USB2524 - Manual (Page 43)

USB MultiSwitch TM Hub
Datasheet
SMSC USB2524 43 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
Pin
100K
Strap High
LED
Pin
+V
LED
LED