Universal Serial Bus InterfaceMCF5253 Reference Manual, Rev. 1Freescale Semiconductor 24-67between the system software and the host controller hardware. Information concerning the initialization ofthe USB modules is included in the following section; however, the full details of the EHCI specificationare beyond the scope of this document.24.9.1 Host Controller InitializationAfter initial power-on or HCReset (hardware or via HCReset bit in the USBCMD register), all of theoperational registers will be at their default values, as illustrated in Table 24-62. After a hardware reset,only the operational registers not contained in the Auxiliary power well will be at their default values.In order to initialize the host controller, the software should perform the following steps:1. Optionally set Streaming Disable in the USBMODE register.2. Optionally modify the BURSTSIZE register.3. Program the PTS field of the PORTSCx register.4. Set the USB_EN bit in the CONTROL register.5. Program the CTRLDSSEGMENT register with 4-Gigabyte segment where all of the interface datastructures are allocated.6. Write the appropriate value to the USBINTR register to enable the appropriate interrupts.7. Write the base address of the Periodic Frame List to the PERIODICLIST BASE register. If thereare no work items in the periodic schedule, all elements of the Periodic Frame List should havetheir T-Bits set.8. Write the USBCMD register to set the desired interrupt threshold, frame list size (if applicable) andturn the controller on via setting the Run/Stop bit.At this point, the host controller is up and running and the port registers begin reporting device connects.The system software can enumerate a port through the reset process (where the port is in the enabled state).At this point, the port is active with SOFs occurring down the enabled port enabled High-speed ports, butthe schedules have not yet been enabled. The EHCI host controller will not transmit SOFs to enabled Full-or Low-speed ports.Table 24-62. Default Values of Operational Register SpaceOperational Register Default Value (after Reset)USBCMD 0x0008_0000USBSTS 0x0000_1000USBINTR 0x0000_0000FRINDEX 0x0000_0000CTRLDSSEGMENT 0x0000_0000PERIODICLISTBASE UndefinedASYNCLISTADDR UndefinedCONFIGFLAG 0x0000_00001PORTSC 0x1c00_0004
