NXP Semiconductors LPC24XX UM10237 - Manual (Page 412)

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User manual Rev. 04 — 26 August 2009 412 of 792
NXP Semiconductors
UM10237
Chapter 15: LPC24XX USB OTG controller
8.1 B-device: peripheral to host switching
In this case, the default role of the OTG controller is peripheral (B-device), and it switches
roles from Peripheral to Host.
The On-The-Go Supplement defines the behavior of a dual-role B-device during HNP
using a state machine diagram. The OTG software stack is responsible for implementing
all of the states in the Dual-Role B-Device State Diagram.
The OTG controller hardware provides support for the state transitions between the states
b_peripheral, b_wait_acon, and b_host in the Dual-Role B-Device state diagram. Setting
B_HNP_TRACK in the OTGStCtrl register enables hardware support for the B-device
switching from peripheral to host. The hardware actions after setting this bit are shown in
Figure 15–60 .
Fig 59. USB OTG controller with software stack
HOST
CONTROLLER
MUX
OHCI
STACK
OTG
STACK
DEVICE
STACK
USB BUS
ISP1302
OTG
CONTROLLER
DEVICE
CONTROLLER
I2C
CONTROLLER