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USB 2.0 Hi-Speed Hub Controller
Datasheet
SMSC USB251x 39 Revision 1.0 (3-11-09)
DATASHEET
8.2.1.8 Register 07h: Configuration Data Byte 2
2:1 CURRENT_SNS Over-Current Sense: Selects current sensing on a port-by-port basis, all
ports ganged, or none (only for bus-powered hubs). The ability to support
current sensing on a port or ganged basis is hardware implementation
dependent.
‘00’ = Ganged sensing (all ports together)
‘01’ = Individual (port-by-port)
‘1x’ = Over-current sensing not supported (must only be used with bus-
powered configurations!)
0 PORT_PWR Port Power Switching: Enables power switching on all ports simultaneously
(ganged), or port power is individually switched on and off on a port- by-port
basis (individual). The ability to support power enabling on a port or ganged
basis is hardware implementation dependent.
‘0’ = Ganged switching (all ports together)
‘1’ = Individual port-by-port switching
BIT
NUMBER BIT NAME DESCRIPTION
7 DYNAMIC Dynamic Power Enable: Controls the ability of the hub to automatically
change from self-powered operation to bus-powered operation if the local
power source is removed or is unavailable (and from bus-powered to self-
powered if the local power source is restored).
When dynamic power switching is enabled, the hub detects the availability
of a local power source by monitoring the external LOCAL_PWR pin. If the
hub detects a change in power source availability, the hub immediately
disconnects and removes power from all downstream devices and
disconnects the upstream port. The hub will then re-attach to the upstream
port as either a bus-powered hub (if local-power is unavailable) or a self-
powered hub (if local power is available).
‘0’ = No dynamic auto-switching
‘1’ = Dynamic auto-switching capable
6 Reserved Reserved
5:4 OC_TIMER OverCurrent Timer: Over-current Timer delay.
‘00’ = 0.1 ms
‘01’ = 4.0 ms
‘10’ = 8.0 ms
‘11’ = 16.0 ms
3 COMPOUND Compound Device: Allows OEM to indicate that the hub is part of a
compound (see the USB specification for definition) device. The applicable
port(s) must also be defined as having a "Non-Removable Device".
Note: When configured via strapping options, declaring a port as non-
removable automatically causes the hub controller to report that it
is part of a compound device.
‘0’ = No
‘1’ = Yes, The hub is part of a compound device
2:0 Reserved Reserved
BIT
NUMBER BIT NAME DESCRIPTION