Universal Serial Bus (USB)MCF5272 ColdFire ® Integrated Microprocessor User’s Manual, Rev. 3Freescale Semiconductor 12-35request with the VEND_REQ interrupt. The user must take the following step to process a class or vendorrequest:1. Read DRR1 and DRR2 to determine the request type.2. If the request has a data stage, the EP0 FIFO should be read or written with the number of bytes asdefined in the DRR2[wLength]. Refer to for more details on accessing the FIFOs.3. When the user has finished processing the request, EP0CTL[CMD_OVER] must be set to signalcompletion of the request. [CMD_ERR] must also be set simultaneously if an error wasencountered while processing the request.12.4.6 REMOTE WAKEUP and RESUME OperationThe MCF5272 supports USB RESUME initiated from three different sources. Two of the sources are forremote wakeup capability. The three different resume mechanisms are listed below:• The user sets EP0CTL[RESUME]. The USB module responds to this only if the USB is in thesuspended state and EP0SR[WAKE_ST] is set. The ColdFire core must be running to writeE0PCTL. To meet USB timing specifications, the RESUME bit must not be set until twomilliseconds have elapsed since the USB module entered suspend state.• The wake-on-ring INT1 interrupt pin is at the active level defined in EP0CTL. The USB moduleresponds to the INT1 pin only if the wake-on-ring function is enabled, the USB is in the suspendedstate and EP0SR[WAKE_ST] is set. The ColdFire core may be powered down, and the resumesignaling wakes up the ColdFire core. The wake-on-ring function must not be enabled until twomilliseconds have elapsed since the USB module entered the suspend state in order to meet USBspecification timing requirements.• The USB module detects any activity on the USB, which may be normal bus activity, resumesignaling, or reset signaling. The ColdFire core may be powered down, and the resume signalingwakes up the ColdFire core.12.4.7 Endpoint Halt FeatureUSB has the ability to halt endpoints due to errors. The user is notified when an endpoint is halted andwhen the halt is cleared. When an endpoint is halted, the user should abort the current transfer andreinitialize the FIFO for the endpoint. An endpoint can be halted for a variety of reasons.• SET _FEATURE request with the endpoint halt feature selector set.• EPnCTL[STALL] is set by the user. This bit should be set only when there is a critical error on theendpoint.• On control endpoints, an error processing a request.A halted endpoint can be cleared in several different ways:• CLEAR _FEATURE request with the endpoint halt feature selector set.• A USB reset signal.• A SET_CONFIGURATION or SET _INTERFACE request.• On control endpoints, a SETUP token for the next request.
