USB2517 datasheet(39/72 Pages) SMSC

39 / 72 page

USB 2.0 Hi-Speed Hub Controller

Datasheet

SMSC USB251x

Revision 1.0 (3-11-09)

DATASHEET

8.2.1.8

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!)

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

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

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

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

BIT

NUMBER

BIT NAME

DESCRIPTION

USB2517 数据表(PDF) 39 Page - SMSC Corporation

USB2517 数据表(HTML) 39 Page - SMSC Corporation

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