STR720 Datasheet, PDF (287/401 Pages) STMicroelectronics – ARM720T 16/32-BIT MCU WITH 16K RAM, USB, CAN, 3 TIMERS, ADC, 6 COMMUNICATIONS INTERFACES

STR720 - USB SLAVE INTERFACE (USB)
Bits 3:0
EP_ID[3:0]: Endpoint Identifier.
These bits are written by the hardware according to the endpoint number, which
generated the interrupt request. If several endpoint transactions are pending,
the hardware writes the endpoint identifier related to the endpoint having the
highest priority defined in the following way: Two endpoint sets are defined, in
order of priority: Isochronous and double-buffered bulk endpoints are
considered first and then the other endpoints are examined. If more than one
endpoint from the same set is requesting an interrupt, the EP_ID bits in
USB_ISTR register are assigned according to the lowest requesting endpoint
register, EP0R having the highest priority followed by EP1R and so on. The
application software can assign a register to each endpoint according to this
priority scheme, so as to order the concurring endpoint requests in a suitable
way. These bits are read only.
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