Superspeed Device Design By Example Pdf 68
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USB was designed to standardize the connection of peripherals to personal computers, both to communicate with and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports and has become commonplace on a wide range of devices. Examples of peripherals that are connected via USB include computer keyboards and mice, video cameras, printers, portable media players, mobile (portable) digital telephones, disk drives, and network adapters.
Released in January 1996, USB 1.0 specified signaling rates of 1.5 Mbit/s (Low Bandwidth or Low Speed) and 12 Mbit/s (Full Speed).[14] It did not allow for extension cables, due to timing and power limitations. Few USB devices made it to the market until USB 1.1 was released in August 1998. USB 1.1 was the earliest revision that was widely adopted and led to what Microsoft designated the "Legacy-free PC".[15][16][17]
A USB device may consist of several logical sub-devices that are referred to as device functions. A composite device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function). An alternative to this is a compound device, in which the host assigns each logical device a distinct address and all logical devices connect to a built-in hub that connects to the physical USB cable.
When a host starts a data transfer, it sends a TOKEN packet containing an endpoint specified with a tuple of (device_address, endpoint_number). If the transfer is from the host to the endpoint, the host sends an OUT packet (a specialization of a TOKEN packet) with the desired device address and endpoint number. If the data transfer is from the device to the host, the host sends an IN packet instead. If the destination endpoint is a uni-directional endpoint whose manufacturer's designated direction does not match the TOKEN packet (e.g. the manufacturer's designated direction is IN while the TOKEN packet is an OUT packet), the TOKEN packet is ignored. Otherwise, it is accepted and the data transaction can start. A bi-directional endpoint, on the other hand, accepts both IN and OUT packets.
USB mice and keyboards can usually be used with older computers that have PS/2 connectors with the aid of a small USB-to-PS/2 adapter. For mice and keyboards with dual-protocol support, an adaptor that contains no logic circuitry may be used: the USB hardware in the keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol. Converters that connect PS/2 keyboards and mice (usually one of each) to a USB port also exist.[53] These devices present two HID endpoints to the system and use a microcontroller to perform bidirectional data translation between the two standards.
Device Firmware Upgrade (DFU) is a vendor- and device-independent mechanism for upgrading the firmware of USB devices with improved versions provided by their manufacturers, offering (for example) a way to deploy firmware bug fixes. During the firmware upgrade operation, USB devices change their operating mode effectively becoming a PROM programmer. Any class of USB device can implement this capability by following the official DFU specifications.[50][54][55]
DFU can also give the user the freedom to flash USB devices with alternative firmware. One consequence of this is that USB devices after being re-flashed may act as various unexpected device types. For example, a USB device that the seller intends to be just a flash drive can "spoof" an input device like a keyboard. See BadUSB.[56]
The design is intended to make it difficult to insert a USB plug into its receptacle incorrectly. The USB specification requires that the cable plug and receptacle be marked so the user can recognize the proper orientation.[23] The USB-C plug however is reversible. USB cables and small USB devices are held in place by the gripping force from the receptacle, with no screws, clips, or thumb-turns as some connectors use.
At first, USB was considered a complement to IEEE 1394 (FireWire) technology, which was designed as a high-bandwidth serial bus that efficiently interconnects peripherals such as disk drives, audio interfaces, and video equipment. In the initial design, USB operated at a far lower data rate and used less sophisticated hardware. It was suitable for small peripherals such as keyboards and pointing devices.
Ethernet standards require electrical isolation between the networked device (computer, phone, etc.) and the network cable up to 1500 V AC or 2250 V DC for 60 seconds.[99] USB has no such requirement as it was designed for peripherals closely associated with a host computer, and in fact it connects the peripheral and host grounds. This gives Ethernet a significant safety advantage over USB with peripherals such as cable and DSL modems connected to external wiring that can assume hazardous voltages under certain fault conditions.[100][101]
To debug a design problem, first you must know it exists. Digital phosphor technology with FastAcq provides you with fast insight into the real operation of your device. Its fast waveform capture rate - greater than 500,000 waveforms per second - gives you a high probability of seeing the infrequent problems common in digital systems: runt pulses, glitches, timing issues, and more. To further enhance the visibility of rarely occurring events, intensity grading indicates how often rare transients are occurring relative to normal signal characteristics.
In the broad sense, any system that processes a signal can be thought of as a filter. For example, an oscilloscope channel operates as a low pass filter where its 3 dB down point is referred to as its bandwidth. Given a waveform of any shape, a filter can be designed that can transform it into a defined shape within the context of some basic rules, assumptions, and limitations.
Digital filters have some significant advantages over analog filters. For example, the tolerance values of analog filter circuit components are high enough that high order filters are difficult or even impossible to implement. High order filters are easily implemented as digital filters. Digital filters can be implemented as Infinite Impulse Response (IIR) or Finite Impulse Response (FIR). The choice of IIR or FIR filters are based upon design requirements and application.
Option6-DJA adds additional jitter analysis capability to better characterize your device's performance. The 31 additional measurements provide comprehensive jitter and eye-diagram analysis and jitter decomposition algorithms, enabling the discovery of signal integrity issues and their related sources in today's high-speed serial, digital, and communication system designs. Option6-DJA also provides eye diagram mask testing for automated pass/fail testing.
A key focus area for embedded designers is testing various embedded and interface technologies for compliance. This ensures the device passes the logo certification at plugfests and achieves successful interoperability when working with other compliant devices.
The instrument contains an optional integrated arbitrary/function generator, perfect for simulating sensor signals within a design or adding noise to signals to perform margin testing. The integrated function generator provides output of predefined waveforms up to 50 MHz for sine, square, pulse, ramp/triangle, DC, noise, sin(x)/x (Sinc), Gaussian, Lorentz, exponential rise/fall, Haversine and cardiac. The AFG can load waveform records up to 128 k points in size from an internal file location or a USB mass storage device.
USB was designed to replace the multitude of cables and connectors required to connect peripheral devices to a host computer. The main goal of USB was to make the addition of peripheral devices quick and easy. All USB devices share some key characteristics to make this possible. All USB devices are self-identifying on the bus. All devices are hot-pluggable to allow for true Plug'n'Play capability. Additionally, some devices can draw power from the USB which eliminates the need for extra power adapters.
USB 1.0 was first introduced in 1996, but was not adopted widely until 1998 with USB 1.1. In 2000, USB 2.0 was released and has since become the de facto standard for connecting devices to computers and beyond. In 2008, the USB specification was expanded with USB 3.0, also known as SuperSpeed USB. USB 3.0 represents a significant change in the underlying operation of USB. To simplify the experience for the user, USB 3.0 has been designed to be plug-n-play backwards compatible with USB 2.0.
A USB device is a peripheral device that connects to the host PC. The range of functionality of USB devices is ever increasing. The device can support either one function or many functions. For example a single multi-function printer may present several devices to the host when it is connected via USB. It can present a printer device, a scanner device, a fax device, etc.
On a full or low-speed bus, if the transaction is repeated, it is repeated in its entirety. This is true regardless of the direction of the data transfer. If the host is requesting information, it will continue to send IN tokens until the device sends data. Until then, the device responds with a NAK, leading to the multitude of IN + NAK pairs that are commonly encountered on a bus. This does not have much consequence as an IN token is only 3 bytes and the NAK is only 1 byte. However, if the host is transmitting data there is the potential for graver consequences. For example, if the host attempted to send 64 bytes of data to a device, but the device responded with a NAK, the host will retry the entire data transaction. This requires sending the entire 64-byte data payload repeatedly until the device responds with an ACK. This has the potential to waste a significant amount of bandwidth. It is for this reason that high-speed hosts have an additional feature when the device signals the inability to accept any more data. 2b1af7f3a8