USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications
Datasheet
8.8
Interrupt Requests (IRQ_N)
The IRQ_N I
2
C request input pin may be used by the SOC when it desires to communicate with the
device during the HUB.Communication stage, assuring the device’s SMBus is active and ready to
respond - even during USB suspend. In order to meet USB suspend current limits, most blocks in the
device, including the SMBus controller, are in a low power state and are not capable of operation.
When the device observes the assertion of IRQ_N, if the device is in suspend mode, it will enable to
PLL and allow serial communication to be achieved. When the IRQ_N pin is negated the device will
return to its normal suspend current consumption. The IRQ_N alternate function can be implemented
at the same time as the INT_N interrupt output, on the same physical pin.
Note:
Asserting the IRQ_N input while the device is in suspend mode will increase the instantaneous
current consumption above the average suspend current requirement. Therefore, this feature
should be used briefly and sparingly.
8.9
Interrupt Output (INT_N)
INT_N is a general interrupt pin intended to communicate select condition changes within the device.
The conditions which may cause an interrupt are detailed in the . The conditions which cause the
interrupt to assert can be controlled through use of the
The general interrupt and all interrupt conditions are functionally latched and event driven. Once the
interrupt or any of the conditions have asserted, the status bit will remain asserted until the SOC
negates the bit using the SMBus. The bits will then remain negated until a new event condition occurs.
The latching nature of the register causes the status to remain even if the condition that caused the
interrupt ceases to be active. The event driven nature of the register causes the interrupt to only occur
when a new event occurs - when a condition is removed and then is applied again. For example, if
the battery charger detection routine has completed and the SOC negates the interrupt status, it will
not cause an interrupt just because the charger detection is still completed. A new charger detection
routine must run before the associated interrupt will assert again.
Revision 1.0 (06-17-13)
56
SMSC USB3813
DATASHEET
SMSC [ SMSC CORPORATION ]
