Chapter 14: Usb Device Controller; Introduction - Philips LPC214 Series User Manual

14.1 Introduction

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 host schedules transactions in 1 ms frames. Each frame contains SoF marker and
transactions that transfer data to/from device endpoints. Each device can have a
maximum of 16 logical or 32 physical endpoints. There are 4 types of transfers defined or
the endpoints. The control transfers are used to configure the device. The interrupt
transfers are used for periodic data transfer. The bulk transfers are used when rate of
transfer is not critical. The isochronous transfers have guaranteed delivery time but no
error correction.
The device controller enables 12 Mb/s data exchange with a USB host controller. It
consists of register interface, serial interface engine, endpoint buffer memory and DMA
controller. The serial interface engine decodes the USB data stream and writes data to the
appropriate end point buffer memory. The status of a completed USB transfer or error
condition is indicated via status registers. An interrupt is also generated if enabled. The
DMA controller when enabled transfers data between the endpoint buffer and the USB
RAM.
Table 172: USB related acronyms, abbreviations and definitions used in this chapter
Acronym/abbreviation Description
AHB
ATLE
ATX
DD
DC
DDP
DMA
EoP
EP
FS
HREADY
LED
LS
MPS
PLL
RAM
SoF
SIE
9397 750 XXXXX
User manual
UM10139

Chapter 14: USB Device Controller

Rev. 01 — 15 August 2005
Advanced High-performance bus
Auto Transfer Length Extraction
Analog Transceiver
DMA Descriptor
Device Core
DD Pointer
Direct Memory Access
End of Package
End Point
Full Speed
When HIGH the HREADY signal indicates that a transfer has finished on
the AHB bus. This signal may be driven LOW to extend a transfer.
Light Emitting Diode
Low Speed
Maximum Packet Size
Phase Locked Loop
Random Access Memory
Start of Frame
Serial Interface Engine
Rev. 01 — 15 August 2005
User manual
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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