Table of Contents
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CHAPTER 29 USB FUNCTION
USB bus connection
detection
Acquiring descriptor
information
Setting device
address
Acquiring descriptor
information (device)
Acquiring descriptor
information
(configuration)
Setting configuration
●
Detecting a connection
The HOST monitors the two signals (D+ and D-) on the USB bus and detects a device connection if a
signal goes to the "H" level.
For the detailed procedure for the case of a self-powered device, see "29.4.1 Detecting Connection and
Disconnection".
●
Example of Register Initialization and Operation Startup Procedure
The following example describes how to initialize the registers and start operation.
1. Set EP0 in the EP0C register (packet size, etc.).
2. Set the EPEN, DIR, and TYPE settings for each endpoint (see EP1C to EP5C registers).
3. Clear the RST bit in the UDCC register.
4. Clear BFINI in the EP0IS, EP0OS, and EP1S to EP5S registers.
5. Clear the HCON bit in the UDCC register.
●
USB bus reset
A bus reset is issued by the HOST PC to initialize the USB device. The USB device must then perform the
following steps: (The first bus reset after USB has been connected does not need any processing.)
1. The USB function is initialized by setting the UDCC register.
2. Transmission/reception buffers in use and related control registers are reset.
3. Firmware control goes to the pre-enumeration state.
754
Figure 29.4-1 Example of Connecting for USB Cable Terminal
Direction
Host
Host
Host
Host
Host
Host
Overview of operation
Device
Operation is not started until the host detects
pull-up on the USB bus.
Device
Data of descriptor is returned to the host.
Device
Any address is divided from the host.
Device
Data of descriptor is returned to the host.
Device
Data of descriptor is returned to the host.
Device
Configuration number is divided from the host.
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