Function Controllers

What is a function controller?

A function controller is used to transmit/receive data to/from a host controller connected with a USB cable. Therefore, communication between function controllers is not possible. Moreover, while communication with a host controller can be performed via a hub controller, direct communication with another function controller connected to a hub controller is not possible.

By equipping peripherals with a function controller, communication with a host controller such as a PC is possible.

What is the relationship between the function controller and driver?

USB functions are classified in device classes by function type, and specifications for the control method and other aspects have been created.

If firmware for a device of a particular class is created, there is a high likelihood that this device can be operated with a class driver already installed in the OS, such as Windows, thereby eliminating the need to develop an original driver.

What are the features of the uPD720122?

The uPD720122 incorporates a USB PHY controller that can automatically switch between high-speed and full-speed, a control endpoint, two bulk endpoints, and an INT endpoint, making this the ideal device for USB high-speed support for storage devices and printing devices.

Can the uPD720122 be used as a full-speed device?

If the host controller operates at full-speed, the uPD720122 can operate at full-speed.
If the host controller operates at high-speed, the uPD720122 operates at high-speed and it cannot be fixed to full-speed.

Can the uPD720122 be used as a low-speed device?

No, it cannot.

Is it necessary to use all three interrupt request signals?

No, it is OK to use just the INT_ALL signal.

Is it possible to design the uPD720122 for bus-powered devices?

This is not recommended since it would be difficult to satisfy the current ratings when unconfigured.