PID field. If a stall interrupt occurs, the pending packet must be dequeued and the
error condition in the target device cleared. If a Reset interrupt occurs (SE0 for more
than 2.5
μ
s), the target has detached.
9. After the TOK_DNE interrupt occurs, the BDTs can be examined and the next data
packet queued by returning to step 2.
42.7 On-The-Go operation
The USB-OTG core provides sensors and controls to enable On-The-Go (OTG)
operation. These sensors are used by the OTG API software to implement the Host
Negotiation Protocol (HNP) and Session Request Protocol (SRP). API calls are provided
to give access to the OTG protocol control signals, and include the OTG capabilities in
the device application. The following state machines show the OTG operations involved
with HNP and SRP protocols from either end of the USB cable.
42.7.1 OTG dual role A device operation
A device is considered the A device because of the type of cable attached. If the USB
Type A connector or the USB Type Mini A connector is plugged into the device, it is
considered the A device.
A dual role A device operates as the following flow diagram and state description table
illustrates.
Chapter 42 Universal Serial Bus Full Speed OTG Controller (USBFSOTG)
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc.
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