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© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
User manual
Rev. 01 — 15 August 2005
194
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.
UM10139
Chapter 14: USB Device Controller
Rev. 01 — 15 August 2005
User manual
Table 172: 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
DDP
DD Pointer
DMA
Direct Memory Access
EoP
End of Package
EP
End Point
FS
Full Speed
HREADY
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.
LED
Light Emitting Diode
LS
Low Speed
MPS
Maximum Packet Size
PLL
Phase Locked Loop
RAM
Random Access Memory
SoF
Start of Frame
SIE
Serial Interface Engine