UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
207 of 362
1.
Introduction
This chapter describes the USB 2.0 High Speed Device interface.
The USB is a 4 wire bus that supports communication between a host and a number (127
max.) of peripherals. The host controller allocates the USB bandwidth to attached devices
through a token based protocol. The bus supports hot plugging, un-plugging and dynamic
configuration of the devices. All transactions are initiated by the host controller.
The interface supports High-speed USB at a bus rate of 480 Mbit/s, as well as Full-speed
USB at 12 Mbit/s.
The host schedules transactions in 1 ms frames. Each frame contains an SoF marker and
transactions that transfer data to/from device endpoints. There are 4 types of transfers
defined for the endpoints. Control transfers are used to configure the device. Interrupt
transfers are used for periodic data transfer. Bulk transfers are used when rate of transfer
is not critical. Isochronous transfers have guaranteed delivery time but no error correction.
The LPC288x USB controller enables 480 or 12 Mbit/s data exchange with a USB host
controller. It includes a USB Controller, a DMA Engine, and a USB 2.0 ATX PHYsical
interface.
The LPC288x USB controller has eight logical endpoints, 0 through 7. Each logical
endpoint contains two physical endpoints for IN and OUT packets
The USB Controller and DMA Engine each have separate blocks of registers in ARM
space.
The USB Controller consists of the protocol engine and buffer management blocks. It
includes an SRAM that is accessible to the DMA Engine and to the processor via the
register interface.
The DMA Engine is an AHB master, having direct access to all ARM memory space but
particularly to on-chip RAM. There are 2 DMA channels, each of which can be assigned to
logical endpoints 1 and 2.
Endpoints with small packet sizes can be handled by software via registers in the USB
Controller. In particular, Control Endpoint 0 is always handled in this way.
2.
Acronyms, abbreviations and definitions
UM10208
Chapter 17: USB Device controller
Rev. 02 — 1 June 2007
User manual
Table 230. USB related acronyms, abbreviations, and definitions used in this chapter
Acronym/abbreviation
Description
AHB
Advanced High-performance bus
ATLE
Auto Transfer Length Extraction
ATX
Analog Transceiver
DD
DMA Descriptor
DC
Device Core