MCF5272 ColdFire ® Integrated Microprocessor User’s Manual, Rev. 3Freescale Semiconductor 12-1Chapter 12Universal Serial Bus (USB)This chapter provides an overview of the USB module of the MCF5272, including detailed operationinformation and the USB programming model. Connection examples and circuit board layoutconsiderations are also provided.The USB Specification, Revision 1.1 is a recommended supplement to this chapter. It can be downloadedfrom http://www.usb.org. Chapter 2 of this specification, Terms and Abbreviations, provides definitions ofmany of the terms found here.NOTEUnless otherwise stated, all mention of the USB specification refers torevision 1.1.12.1 IntroductionThe universal serial bus (USB) is an industry-standard extension to the PC architecture. The USBcontroller on the MCF5272 supports device mode data communication between itself and a USB hostdevice, typically a PC. One host and up to 127 attached peripherals share USB bandwidth through ahost-scheduled, token-based protocol. The USB uses a tiered star topology with a hub at the center of eachstar, as shown in Figure 12-1. Each wire segment is a point-to-point connection between the host Aconnector and a peripheral B connector.The USB cables contain four wires, two for data and two for power. The USB full-speed bit rate is12 Mbps. A limited-capability, low-speed mode is also defined at 1.5 Mbps.The MCF5272 includes the following features:• Supports full-speed 12-Mbps USB devices and low-speed 1.5-Mbps devices• Full compliance with the Universal Serial Bus Specification, Revision 1.1• Automatic processing of USB standard device requests: CLEAR _FEATURE, GET _CONFIGURATION ,GET _DESCRIPTOR, GET _INTERFACE, GET_STATUS , SET _ADDRESS, SET_CONFIGURATION,SET _FEATURE , and SET _INTERFACE• Supports either internal or external USB transceiver• Programmable 512-byte receive and 512-byte transmit FIFO buffers• USB device controller with protocol control and administration for up to eight endpoints, 16interfaces, and 16 configurations• Programmable endpoint types with support for up to eight control, interrupt, bulk, or isochronousendpoints• Independent interrupts for each endpoint
