USB3813 datasheet(43/57 Pages) MICROCHIP

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USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications

Datasheet

 2014 Microchip Technology Inc.

DS00001715A-page 43

8.8

Interrupt Requests (IRQ_N)

The IRQ_N I2C 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 Serial Port Interrupt Mask Register.

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.

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