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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
156 of 571
NXP Semiconductors
UM10316
Chapter 13: LPC29xx USB device
5.8 GoodLink
Good USB connection indication is provided through GoodLink technology. When the
device is successfully enumerated and configured, the LED indicator will be permanently
ON. During suspend, the LED will be OFF.
This feature provides a user-friendly indicator on the status of the USB device. It is a
useful field diagnostics tool to isolate faulty equipment.
To use the GoodLink feature the UP_LED signal should control an LED. The UP_LED
signal is controlled using the SIE Configure Device command.
6.
Operational overview
Transactions on the USB bus transfer data between device endpoints and the host. The
direction of a transaction is defined with respect to the host. OUT transactions transfer
data from the host to the device. IN transactions transfer data from the device to the host.
All transactions are initiated by the host controller.
For an OUT transaction, the USB ATX receives the bi-directional D+ and D- signals of the
USB bus. The Serial Interface Engine (SIE) receives the serial data from the ATX and
converts it into a parallel data stream. The parallel data is written to the corresponding
endpoint buffer in the EP_RAM.
For IN transactions, the SIE reads the parallel data from the endpoint buffer in EP_RAM,
converts it into serial data, and transmits it onto the USB bus using the USB ATX.
Once data has been received or sent, the endpoint buffer can be read or written. How this
is accomplished depends on the endpoint’s type and operating mode. The two operating
modes for each endpoint are Slave (CPU-controlled) mode, and DMA mode.
In Slave mode, the CPU transfers data between RAM and the endpoint buffer using the
Register Interface. See
Section 13–13 “Slave mode operation”
for a detailed description of
this mode.
In DMA mode, the DMA transfers data between RAM and the endpoint buffer. See
for a detailed description of this mode.
7.
Pin description
Table 115. USB external interface
Name
Direction
Description
V
BUS
I
V
BUS
status input. When this function is not enabled
via its corresponding PINSEL register, it is driven
HIGH internally.
USB_CONNECT
O
SoftConnect control signal.
USB_UP_LED
O
GoodLink LED control signal.
USB_D+
I/O
Positive differential data.
USB_D-
I/O
Negative differential data.