USB2503 datasheet(34/46 Pages) SMSC

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USB 2.0 High-Speed 4-Port Hub Controller

Datasheet

Revision 1.92 (05-08-07)

SMSC USB2514

DATASHEET

4.4.4

Slave Device Time-Out

According to the SMBus Specification, V1.0 devices in a transfer can abort the transfer in progress

and release the bus when any single clock low interval exceeds 25ms (TTIMEOUT, MIN). Devices that

have detected this condition must reset their communication and be able to receive a new START

condition no later than 35ms (TTIMEOUT, MAX).

Note: Some simple devices do not contain a clock low drive circuit; this simple kind of device typically

resets its communications port after a start or stop condition. The Slave Device Time-Out must

be implemented.

4.4.5

Stretching the SCLK Signal

The Hub supports stretching of the SCLK by other devices on the SMBus. The Hub does not stretch

the SCLK.

4.4.6

SMBus Timing

The SMBus Slave Interface complies with the SMBus AC Timing Specification. See the SMBus timing

in the “Timing Diagram” section.

4.4.7

Bus Reset Sequence

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

immediately by a STOP field.

4.4.8

SMBus Alert Response Address

The SMBALERT# signal is not supported by the Hub.

4.4.8.1

Undefined Registers

The registers shown in Table 4.2 are the defined registers in the Hub. Reads to undefined registers

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

4.4.8.2

Reserved Registers

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

4.5

Default Configuration Option:

The SMSC Hub can be configured via its internal default configuration. (please see Section 4.3.1,

"Internal Register Set (Common to EEPROM and SMBus)" for specific details on how to enable default

configuration.)

Please refer to Table 4.2 for the internal default values that are loaded when this option is selected.

4.6

Default Strapping Options:

The USB2514 can be configured via a combination of internal default values and pin strap options.

Please see Table 3.1 and Table 3.2 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 4.2 for the internal default values that are loaded when this option is selected.

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