1. Technical Field
The present invention relates to a data transfer control device and electronic equipment.
2. Related Art
In recent years, there has been a strong demand for peripheral equipment with a universal serial bus (USB) function such as cellular phones and mobile audio devices. JP-A-2002-55936 is an example of related art. The example describes a hitherto known technique of the data transfer control device realizing the host function of the peripheral equipment. In addition to the example, there is USB On-The-Go (OTG) standard as such technique.
When the data transfer control device embedded with the peripheral equipment performs the host function, the data transfer control device has to conduct a state control as a host.
However, in the state control of the host, so many kinds of states exist, and complicated processes to control or detect a line state corresponding to each state are required. This causes a problem of increase in the size of circuits and a problem of complex design when hardware tries to perform all the state control.
Meanwhile, when firmware (software) that a central processing unit (CPU) runs on tries to perform all the state control, the firmware has to control and detect all the line states corresponding to each state. This causes a problem that designing of the firmware becomes complex and the state control process will not finish within a predetermined time period. Furthermore, the CPU embedded with the peripheral equipment generally has a low processing capacity compared to that of the CPU embedded with a personal computer (PC). Therefore, when the firmware tries to process all the state control, processing load of the CPU increases and this leads to a problem such that speeding up of the data transfer is impaired and the performance of the whole equipment is deteriorated.