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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
139 of 368
NXP Semiconductors
UM10375
Chapter 10: LPC13xx USB device controller
10.6.5 Register interface
The Register Interface allows the CPU to control the operation of the USB Device
Controller. It also provides a way to write transmit data to the controller and read receive
data from the controller.
10.6.6 SoftConnect
The connection to the USB is accomplished by bringing USB_DP (for a full-speed device)
HIGH through a 1.5 kOhm pull-up resistor. The SoftConnect feature can be used to allow
software to finish its initialization sequence before deciding to establish connection to the
USB. Re-initialization of the USB bus connection can also be performed without having to
unplug the cable.
To use the SoftConnect feature, the USB_CONNECT signal should control an external
switch that connects the 1.5 kOhm resistor between USB_DP and 3.3 V. Software can
then control the USB_CONNECT signal by writing to the CON bit using the SIE Set
Device Status command.
10.7 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.
Fig 17. USB SoftConnect interfacing
LPC134x
USB-B
connector
USB_DP
USB_CONNECT
soft-connect switch
USB_DM
USB_VBUS
V
SS
V
DD
R1
1.5 k
Ω
RS = 33
Ω
002aae608
RS = 33
Ω