MPC8280 datasheet(817/1386 Pages) FREESCALE

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MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

27-1

Chapter 27

Universal Serial Bus Controller

The universal serial bus (USB) controller allows the MPC8280 to communicate with other devices via a

USB connection. This chapter describes the MPC8280’s USB controller, including basic operation, the

parameter RAM, and registers. It also provides programming examples for initializing host mode and

function mode of the USB controller.

27.1

USB Integration in the MPC8280

The following restrictions apply when enabling the USB controller in the MPC8280:

•

The USB peripheral and SCC4 are mutually exclusive: it is not legal to enable both peripherals at

the same time.

•

The USB controller pins are multiplexed with SCC4 pins in the parallel I/O. Refer to Chapter 41,

“Parallel I/O Ports.” The user programs the parallel I/O registers as if scc4 was being used. If the

USB controller is enabled, the signals are automatically routed to the USB controller instead of

SCC4.

•

The USB controller uses the transmit clock of SCC4 as its clock. The user must program

CMXSCR[T4CS] (refer to Section 16.4.6, “CMX SMC Clock Route Register (CMXSMR)”) to the

desired source for USB when the USB controller is enabled.

•

The user must clear CMXSCR[SC4] (refer to Section 16.4.5, “CMX SCC Clock Route Register

(CMXSCR)) when the USB controller is enabled.

27.2

Overview

The universal serial bus (USB) is an industry-standard extension to the PC architecture. The USB

controller on the MPC8280 supports data exchange between a wide range of simultaneously accessible

peripherals. Attached peripherals share USB bandwidth through a host-scheduled, token-based protocol.

The USB physical interconnect is a tiered-star topology, and the center of each star is a hub. Each wire

segment is a point-to-point connection between the host and a hub or function, or a hub connected to

another hub or a function. The USB transfers signal and power over a four-wire cable, and the signaling

occurs over two wires and point-to-point segments. The USB full speed signaling bit rate is 12 Mbps. Also,

a limited capability low-speed signaling mode is defined at 1.5 Mbps. Refer to the USB Specification

Revision 2.0 for further details. It can be downloaded from http://www.usb.org.

The MPC8280 USB controller consists of a transmitter module, receiver module, and two protocol state

machines. The protocol state machines control the receiver and transmitter modules. One state machine

implements the function state diagram and the other implements the host state diagram. The USB

controller can implement a USB function endpoint, a USB host, or both for testing purposes (loop-back

diagnostics).

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