Datasheet
USB 2.0 Hi-Speed 7-Port Hub Controller
Datasheet
SMSC USB2517 39 Revision 2.8 (09-17-12)
DATASHEET
7.3.2 Invalid Protocol Response Behavior
Registers 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.
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. See Section 7.3.3 for the response to undefined registers.
7.3.3 General Call Address Response
The Hub does not respond to a general call address of 0000_000b.
7.3.4 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 (T
TIMEOUT, MIN
). Devices that have detected this condition must
reset their communication and be able to receive a new START condition no later than 35ms (T
TIMEOUT, 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.
7.3.5 Stretching the SCLK Signal
The Hub supports stretching of the SCLK by other devices on the SMBus. The Hub does not stretch the SCLK.
7.3.6 SMBus Timing
The SMBus Slave Interface complies with the SMBus AC Timing Specification. See the SMBus timing in the “Timing
Diagram” section.
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
The registers shown in Table 7.1 are the defined registers in the Hub. Reads to undefined registers return to 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 Configuration Option:
The SMSC Hub can be configured via its internal default configuration. (Please see Section 7.2.1, "Internal Register
Set (Common to EEPROM and SMBus)" for specific details on how to enable default configuration.)
Please refer to Tabl e 7. 1 for the internal default values that are loaded when this option is selected.
7.5 Default Strapping Options:
The USB2517 can be configured via a combination of internal default values and pin strap options. Please see
Table 5.1, "PIN Descriptions" and Table 5.2, "USB2517 SMBUS or EEPROM Interface Behavior" 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 Ta bl e 7. 1 for the internal
default values that are loaded when this option is selected.