USB2517-JZX datasheet(54/72 Pages) SMSC

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USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 1.0 (3-11-09)

SMSC USB251x

DATASHEET

8.3.2.2

Block Read

A block read differs from a block write in that the repeated start condition exists to satisfy the I2C

specification’s requirement for a change in the transfer direction.

Figure 8.2 Block Read

8.3.3

Invalid Protocol Response Behavior

Registers that are accessed with an invalid protocol are not updated. A register is only updated

following a valid protocol. The only valid protocols are write block and read block, which are described

above. The hub only responds to the hardware selected Slave Address (0101100x).

Attempting to communicate with the hub over SMBus with an invalid slave address or invalid protocol

results in no response, and the SMBus Slave Interface returns to the idle state.

The only valid registers that are accessible by the SMBus slave address are the registers defined in

the Registers Section. The hub does not respond to undefined registers.

8.3.4

General Call Address Response

The hub does not respond to a general call address of 0000_000b.

8.3.5

Slave Device Time-Out

According to the SMBus specification, version 1.0 devices in a transfer can abort the transfer in

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

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

START condition no later than 35 ms (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.

8.3.6

Stretching the SCLK Signal

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

the SCLK.

8.3.7

SMBus Timing

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

in the “Timing Diagram” section.

8.3.8

Bus Reset Sequence

The SMBus slave interface resets and returns to the idle state upon a START field followed

immediately by a STOP field.

Block Read

Slave Address

Byte Count = N

Data byte 1

Data byte 2

Data byte N

...

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