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USBN9603 Fiches technique(PDF) 22 Page - National Semiconductor (TI) |
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USBN9603 Fiches technique(HTML) 22 Page - National Semiconductor (TI) |
22 / 60 page 22 www.national.com 6.0 Functional Description 6.1 FUNCTIONAL STATES 6.1.1 Line Condition Detection At any given time, the USBN9603 is in one of the following states (see Section 6.1.2 for the functional state transitions): • NodeOperational Normal operation • NodeSuspend Device operation suspended due to USB inactivity • NodeResume Device wake-up from suspended state • NodeReset Device reset The NodeSuspend, NodeResume, or NodeReset line condition causes a transition from one operating state to another. These conditions are detected by specialized hardware and reported via the Alternate Event (ALTEV) register. If interrupts are enabled, an interrupt is generated upon the occurrence of any of the specified conditions. NodeOperational This is the normal operating state of the device. In this state, the node is configured for operation on the USB bus. NodeSuspend A USB device is expected to enter NodeSuspend state when 3 mS have elapsed without any detectable bus activity. The USBN9603 looks for this event and signals it by setting the SD3 bit in the ALTEV register, which causes an interrupt, if en- abled, to be generated. The firmware should respond by putting the USBN9603 in NodeSuspend state. IThe USBN9603 can resume normal operation under firmware control in response to a local event at the host controller. It can wake up the USB bus via a NodeResume, or when detecting a resume command on the USB bus, which signals an interrupt to the host controller. NodeResume If the host has enabled remote wake-ups from the node, the USBN9603 can initiate a remote wake-up. Once the firmware detects the event, which wakes up the bus, it releases the USBN9603 from NodeSuspend state by initi- ating a NodeResume on the USB using the NFSR register. The node firmware must ensure at least 5 mS of Idle on the USB. While in NodeResume state, a constant “K” is signalled on the USB. This should last for at least 1 mS and no more than 5 mS, after which the USB host should continue sending the NodeResume signal for at least an additional 20 mS, and then completes the NodeResume operation by issuing the End Of Packet (EOP) sequence. To successfully detect the EOP, the firmware must enter USB NodeOperational state by setting the NFSR register. If no EOP is received from the host within 100 mS, the software must reinitiate NodeResume. NodeReset When detecting a NodeResume or NodeReset signal while in NodeSuspend state, the USBN9603 can signal this to the main controller by generating an interrupt. USB specifications require that a device must be ready to respond to USB tokens within 10 mS after wake-up or reset. 6.1.2 Functional State Transition Figure 18 shows the device states and transitions, as well as the conditions that trigger each transition. All USBN9603 state transitions are initiated by the firmware. |
Numéro de pièce similaire - USBN9603 |
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Description similaire - USBN9603 |
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