USB2504_06 datasheet(27/46 Pages) SMSC

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Integrated USB 2.0 Compatible 4-Port Hub

Datasheet

SMSC USB2504/USB2504A

Revision 2.1 (12-06-06)

DATASHEET

5.3.4

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.

5.3.5

Stretching the SCLK Signal

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

the SCLK.

5.3.6

SMBus Timing

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

in the “Timing Diagram” section.

5.3.7

Bus Reset Sequence

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

immediately by a STOP field.

5.3.8

SMBus Alert Response Address

The SMBALERT# signal is not supported by the Hub.

5.3.9

Internal SMBus Memory Register Set

The following table provides the SMBus slave interface register map values.

Table 5.4 SMBus Slave Interface Register Map

REG

ADDR

R/W

ABBR

BIT 7

(MSB)

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

(LSB)

00h

R/W

Status/Command

STCD

01h

R/W

VID LSB

VIDL

02h

R/W

VID MSB

VIDM

654

03h

R/W

PID LSB

PIDL

04h

R/W

PID MSB

PIDM

654

05h

R/W

DID LSB

DIDL

06h

R/W

DID MSB

DIDM

07h

R/W

Config Data Byte 1

CFG1

08h

R/W

Config Data Byte 2

CFG2

09h

R/W

Non-Removable

Devices

NRD

0Ah

R/W

Port Disable (Self)

PDS

0Bh

R/W

Port Disable (Bus)

PDB

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