SCM USB data removable storage functionality, including USB host interface hardware design and firmware design of the whole USB drive. The design of the drive firmware specific and contains several protocol implementations: USB1.1 Control Transmission Protocol, USB BULK transfer protocol, USB mass storage class protocol, the UFI disk operations command and FAT file system standard. USB (Universal Serial Bus) USB interface peripherals (device) is used to connect to the host (host), data transfer between external bus architecture, is a fast, flexible bus interface, USB transmission type of control (control), batch (bulk), interrupt (interrupt) and synchronous (synchronous) transmission, its greatest feature is easy to use, plug and play, mainly used in medium-speed and low-speed peripherals. The blue ray green laser pointer must be very expensive.
Control data is used to configure the USB access bus, the other driver software can choose to use depending on the application to control the transmission of this data transmission without losing data. Typical bulk data, including the large amount of data like a printer or scanner data, bulk data is continuous error detection functions implemented in hardware, and optionally should enter retry operation at the hardware level to ensure reliable data exchange. Spontaneously generated by the device data transmission is interrupted data transmission, the type of data transmission can be initiated at any time by the USB device, the transmission rate of not less than the device and the USB bus. If the relevant materials haven’t been exploited yet, there will be no chance for we to see some new types of green laser pointer .
The synchronous data is continuous and real-time to generate, transmit and process included in the stability of the synchronization data to send and receive rate clock in order to maintain the timing relationship, synchronous data transmission must be in accordance with the rate received. Firmware and enumeration. All transfers are started by the host, the firmware is designed to completely interrupt-driven, when the CPU processing the foreground task, the USB transmission in the background. This ensures the best transmission rate and better software architecture. USB host system firmware to write more complicated, mainly related to the USB control transfer, the preparation of the USB bulk transfer, mass storage class protocol, the UFI disk operations command and FAT file system. green laser pointer is the LED torch.
All the lowest operating procedures, there is no ready-made library support, so the structure of the program overall framework and protocol-specific data structure of the organization is critical. The module design of the main difficulty lies in the preparation of the software program, the agreement involved in the preparation of the program should pay attention to the idea of modular, each specific agreement as far as possible to write in a source file, data structures, constants, variables well defined in the header file for each module. The debugging USB underlying control transfer can take full advantage of Bus Hound tool to grab the USB removable storage into the computer communicate with the computer data analysis, comparison and reference development, deepen the understanding of the USB low-level information exchange. green laser pointer is the 3 in 1 type.
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