Bus interface and computer communication (quad) USB external bus

Introduction to USB

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USB? is English universal? Serial? Bus (universal serial bus) abbreviation, is an external bus standard, used to regulate the connection and communication between the computer and external devices, is applied in the field of PC interface technology. USB interface supports plug-and-use and hot-swap functions for devices.

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1. The topological structure of USB?

1)? Does the USB? Network protocol have only one host for each USB system? Is it responsible for managing the entire USB system, including USB? Connection and removal of Device, with USB? Device communication, the control of the general line, etc.?

2)? Is there a root on the Host side? Hub, one or more USB downlink ports can be supplied with one USB connection per port? Hub? or a USB? Device?

3)? Usb? Hub? Is it for USB port extension, i.e. USB? Hub? You can extend a USB port to multiple ports. Is every func (Function) in a USB? Device, such as USB keyboard, USB mouse, USB? MODEM,? USB, HDD, etc.?

4)? Compound? Device? refers to a hub? And one or more non-deleted USB? Device? 5)? A USB? System can connect up to 127 function?

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1. ? What type of device is USB? (device?class)?

   Although the USB device will show some basic features of USB, the USB device can be divided into several different types. Devices of the same type can have some common behavioral characteristics and work protocols to make the device's drive sequence easier to write. The following table gives some basic USB device type classification

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2. ? The electrical characteristics of USB?

   USB connector contains four lines: 2? Strip for power supply (VBUS and GND), 2 bar for USB data transfer (d+ and D). VBUS 5 V power supply with a current of up to 500mA. D+ and D are bidirectional signal lines with a signal transmission rate of 12Mbps? (83ns per person). d+ and D-signal level is 3.3V?

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3. What are the features of USB?

   1) USB? Provides a single, easy-to-use standard connection type for all USB peripherals. This simplifies the design of USB peripherals to achieve a single data universal interface?

   2) The entire USB system has only one port and one interrupt to save system resources ?

   3) USB? Hot-swappable (Hot?plug) and PnP (Plug-and-play), which means you can safely plug in and disconnect USB devices without shutting down your PC?

   4) USB? Provides flexibility in device power supply. Is it connected directly to the hub, or is it a device connected to the host? can be powered by USB or by battery or other power devices, or by using two power supply combinations? and support energy-saving hang-up and wake-up modes?

   5) USB? transfer rate ? adapt to a variety of different types of peripherals, the rate of full-speed 12Mbps, and low-speed 1.5Mbps? USB2.0 also support the high speed transfer rate of 480Mbps?

   6) in order to meet the requirements of different types of peripherals, USB provides four different types of data transmission: control transmission, Bulk? Data transmission, interrupt data transmission and synchronous data transmission, synchronous data transmission for audio and video? Provide fixed bandwidth for real-time data transmission of real-time devices?

   7) USB port has very flexible scalability, a USB port is connected to a USB? Hub? can be extended to multiple USB ports

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4. What are the features of USB?

   1) USB? Provides a single, easy-to-use standard connection type for all USB peripherals. This simplifies the design of USB peripherals to achieve a single data universal interface?

   2) The entire USB system has only one port and one interrupt to save system resources?

   3) USB? Hot-swappable (Hot?plug) and PnP (Plug-and-play), which means you can safely plug in and disconnect USB devices without shutting down your PC?

   4) USB? Provides flexibility in device power supply. Is it connected directly to the hub, or is it a device connected to the host? can be powered by USB or by battery or other power devices, or by using two power supply combinations? and support energy-saving hang-up and wake-up modes?

   5) USB? Provides speed of full 12Mbps and low speed 1.5Mbps? To accommodate a variety of different types of peripherals? USB2.0? also supports 480Mbps high-speed transfer rate?

   6) in order to meet the requirements of different types of peripherals, USB provides four different types of data transmission: control, Bulk? data transmission, interrupt data transmission and synchronous data transmission, synchronous data transmission provides fixed bandwidth for real-time data transmission of audio and video?

   7) USB port has very flexible scalability, a USB port is connected to a USB? Hub? can be extended to multiple USB ports??

   How about 7.USB transmission?

   USB? There are four kinds of transmission modes:?? 1) control mode of transmission:?

   Control transmission is two-way transmission of data, mainly for query configuration and to the USB device to send generic commands. Control transmission? The method can include 8,16,32 and 64 bytes of data, which depends on the device and the transfer speed. Control transmission typically used? Transmission between the host computer and the USB peripheral endpoint? 2) synchronous (isochronous) transmission mode:?

   Synchronous transmission provides a defined bandwidth and interval, which is used for time-intensive and robust fault-tolerant streaming data, or for instant applications that require a constant data rate, such as a VoIP call that performs an instant call? Is it a good choice to use synchronous transfer mode when applying? 3) Interrupt (interrupt ) mode transfer:?

   Interrupt mode transmission is mainly used to check whether the device has interrupt data to be transmitted. The structure of the endpoint mode of the device? Determines its query frequency from 1 to 255ms? This type of transmission is typically applied in a small amount of scattered and unpredictable data transmission, keyboard, joystick and mouse belong to this category? 4) Bulk (bulk) transfer:?

   The main application is the large amount of data transmission, and the transmission and reception of data without bandwidth and time-interval requirements. Printers and scanners belong to this type.

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   Reference:

6. Common Interface Circuit Introduction

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Bus interface and computer communication (quad) USB external bus