2-Port USB 2.0 Hub Controller

Datasheet

5.2.3.12EEPROM Offset E(h) - Hub Controller Max Current For Bus Powered Operation

BIT

 

 

NUMBER

BIT NAME

DESCRIPTION

 

 

 

7:0

HC_MAX_C_BP

Hub Controller Max Current Bus-Powered: Value in 2mA increments that the

 

 

Hub consumes from an upstream port (VBUS) when operating as a self-

 

 

powered hub. This value includes the hub silicon along with the combined

 

 

power consumption (from VBUS) of all associated circuitry on the board.

 

 

This value does NOT include the power consumption of a permanently

 

 

attached peripheral if the hub is configured as a compound device.

 

 

A value of 50 (decimal) indicates 100mA, which is the default value.

 

 

 

5.2.3.13EEPROM Offset F(h) - Power-On Time

BIT

 

 

NUMBER

BIT NAME

DESCRIPTION

 

 

 

7:0

POWER_ON_TIME

Power On Time: The length of time that is takes (in 2 ms intervals) from the

 

 

time the host initiated power-on sequence begins on a port until power is

 

 

good on that port.

 

 

 

5.3SMBus Slave Interface

Instead of loading User-Defined Descriptor data from an external EEPROM, the SMSC Hub can be configured to receive a code load from an external processor via an SMBus interface. The SMBus interface shares the same pins as the EEPROM interface, if CFG_SEL1 & CFG_SEL0 activates the SMBus interface, external EEPROM support is no longer available (and the user-defined descriptor data must be downloaded via the SMBus). Due to system issues, the SMSC Hub waits indefinitely for the SMBus code load to complete and only “appears” as a newly connected device on USB after the code load is complete.

The Hub’s SMBus implementation is a subset of the SMBus interface to the host. The device is a slave-onlySMBus device. The implementation in the device is a subset of SMBus since it only supports two protocols.

The Write Byte and Read Byte protocols are the only valid SMBus protocols for the Hub. The Hub responds to other protocols as described in Section 5.3.2, "Invalid Protocol Response Behavior," on page 25. Reference the System Management Bus Specification, Rev 1.0.

The SMBus interface is used to read and write the registers in the device. The register set is shown in Section 5.3.9, "Internal SMBus Memory Register Set," on page 26.

5.3.1Bus Protocols

Typical Write Byte and Read Byte protocols are shown below. Register accesses are performed using 7-bit slave addressing, an 8-bit register address field, and an 8-bit data field. The shading indicates the Hub driving data on the SMBDATA line; otherwise, host data is on the SDA/SMBDATA line.

The slave address is the unique SMBus Interface Address for the Hub that identifies it on SMBus. The register address field is the internal address of the register to be accessed. The register data field is the data that the host is attempting to write to the register or the contents of the register that the host is attempting to read.

Note: Data bytes are transferred MSB first (msb first).

Revision 2.3 (08-27-07)

24

SMSC USB2502

 

DATASHEET