romikgosai/squad_modified_2 huggingface dataset:
USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to the delays from connecting cables, the maximum acceptable delay per cable amounts to 26 ns. The USB 2.0 specification requires that cable delay be less than 5.2 ns per meter (192 000 km/s, which is close to the maximum achievable transmission speed for standard copper wire).

Q1: How long is the maximum cable length the USB 2.0 provides?
A1: 5 meters for devices running at Hi Speed
Q2: What is the maximum acceptable delay per cable?
A2: 26 ns
Q3: What does theUSB 2.0 specification require?
A3: cable delay be less than 5.2 ns per meter
A unit load is defined as 100 mA in USB 1.x and 2.0, and 150 mA in USB 3.0. A device may draw a maximum of five unit loads from a port in USB 1.x and 2.0 (500 mA), or six unit loads in USB 3.0 (900 mA). There are two types of devices: low-power and high-power. A low-power device (such as a USB HID) draws at most one-unit load, with minimum operating voltage of 4.4 V in USB 2.0, and 4 V in USB 3.0. A high-power device draws, at most, the maximum number of unit loads the standard permits. Every device functions initially as low-power (including high-power functions during their low-power enumeration phases), but may request high-power, and get it if available on the providing bus.

Q1: What is a unit load defined as?
A1: 100 mA in USB 1.x and 2.0
Q2: How much is a unit load in USB 3.0?
A2: 150 mA
Q3: What is the maximum amount of load a USB 1. and 2.0 device may draw?
A3: five unit loads
Q4: What is the maximum amount of load a USB 3.0 device may draw?
A4: six unit loads
Some devices, such as high-speed external disk drives, require more than 500 mA of current and therefore may have power issues if powered from just one USB 2.0 port: erratic function, failure to function, or overloading/damaging the port. Such devices may come with an external power source or a Y-shaped cable that has two USB connectors (one for power and data, the other for power only) to plug into a computer. With such a cable, a device can draw power from two USB ports simultaneously. However, USB compliance specification states that "use of a 'Y' cable (a cable with two A-plugs) is prohibited on any USB peripheral", meaning that "if a USB peripheral requires more power than allowed by the USB specification to which it is designed, then it must be self-powered."

Q1: What is an example of a device that requires more than 500 mA of current?
A1: high-speed external disk drives
Q2: What is an issue that may occur if a high-speed external disk drive is powered from just one USB 2.0 port.
A2: may have power issues
Q3: What does USB compliance specification prohibit?
A3: "use of a 'Y' cable (a cable with two A-plugs)
The USB Battery Charging Specification Revision 1.1 (released in 2007) defines a new type of USB port, called the charging port. Contrary to the standard downstream port, for which current draw by a connected portable device can exceed 100 mA only after digital negotiation with the host or hub, a charging port can supply currents between 500 mA and 1.5 A without the digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drops its output voltage if the portable device attempts to draw more than the rated current. The charger port may shut down if the load is too high.

Q1: What defines a new type of USB port, called the charging port?
A1: The USB Battery Charging Specification Revision 1.1
Q2: When was the USB Battery Charging Specification Revision 1.1 released?
A2: in 2007
Q3: What was the USB Battery Charging Specification Revision 1.1 called?
A3: the charging port
Q4: What does a charging port supply?
A4: up to 500 mA at 5 V
Two types of charging port exist: the charging downstream port (CDP), supporting data transfers as well, and the dedicated charging port (DCP), without data support. A portable device can recognize the type of USB port; on a dedicated charging port, the D+ and D− pins are shorted with a resistance not exceeding 200 ohms, while charging downstream ports provide additional detection logic so their presence can be determined by attached devices. (see ref pg. 2, Section 1.4.5, & Table 5-3 "Resistances"—pg. 29).

Q1: How many types of charging ports exist?
A1: Two types
Q2: What can a portable device recognize?
A2: the type of USB port
Q3: What are the D+ and D- shortened with?
A3: a resistance not exceeding 200 ohms
The USB Battery Charging Specification Revision 1.2 (released in 2010) makes clear that there are safety limits to the rated current at 5 A coming from USB 2.0. On the other hand, several changes are made and limits are increasing including allowing 1.5 A on charging downstream ports for unconfigured devices, allowing high speed communication while having a current up to 1.5 A, and allowing a maximum current of 5 A. Also, revision 1.2 removes support for USB ports type detection via resistive detection mechanisms.

Q1: What does the USB Battery Charging Specification Revision 1.2 make clear of?
A1: there are safety limits to the rated current at 5 A coming from USB 2.0
Q2: What does revision 1.2 remove?
A2: USB ports type detection via resistive detection mechanisms
Q3: When was USB Battery Charging Specification Revision 1.2 released?
A3: in 2010
In July 2012, the USB Promoters Group announced the finalization of the USB Power Delivery ("PD") specification, an extension that specifies using certified "PD aware" USB cables with standard USB Type-A and Type-B connectors to deliver increased power (more than 7.5 W) to devices with larger power demand. Devices can request higher currents and supply voltages from compliant hosts –  up to 2 A at 5 V (for a power consumption of up to 10 W), and optionally up to 3 A or 5 A at either 12 V (36 W or 60 W) or 20 V (60 W or 100 W). In all cases, both host-to-device and device-to-host configurations are supported.

Q1: When did the USB Promoters Group announce the finalization of the USB Power Delivery specification?
A1: In July 2012
Q2: What can devices request?
A2: higher currents and supply voltages from compliant hosts
Q3: In all cases, both host-to-device and device-to-host configurations are what?
A3: supported
The USB Power Delivery revision 2.0 specification has been released as part of the USB 3.1 suite. It covers the Type-C cable and connector with four power/ground pairs and a separate configuration channel, which now hosts a DC coupled low-frequency BMC-coded data channel that reduces the possibilities for RF interference. Power Delivery protocols have been updated to facilitate Type-C features such as cable ID function, Alternate Mode negotiation, increased VBUS currents, and VCONN-powered accessories.

Q1: The USB Power Delivery revision 2.0 specification has been released as part of what?
A1: USB 3.1
Q2: What does the USB Power Delivery revision 2.0 specification cover?
A2: Type-C cable and connector with four power/ground pairs and a separate configuration channel
Q3: Power delivery protocols have been updated to facilitate what?
A3: Type-C features
Sleep-and-charge USB ports can be used to charge electronic devices even when the computer is switched off. Normally, when a computer is powered off the USB ports are powered down, preventing phones and other devices from charging. Sleep-and-charge USB ports remain powered even when the computer is off. On laptops, charging devices from the USB port when it is not being powered from AC drains the laptop battery faster; most laptops have a facility to stop charging if their own battery charge level gets too low.

Q1: What can sleep-and-charge USB ports be used to do?
A1: charge electronic devices even when the computer is switched off
Q2: What is normally powered off whenever the computer is off?
A2: USB ports
Q3: What remain powered even whenever the computer is powered off?
A3: Sleep-and-charge USB ports
On Dell and Toshiba laptops, the port is marked with the standard USB symbol with an added lightning bolt icon on the right side. Dell calls this feature PowerShare, while Toshiba calls it USB Sleep-and-Charge. On Acer Inc. and Packard Bell laptops, sleep-and-charge USB ports are marked with a non-standard symbol (the letters USB over a drawing of a battery); the feature is simply called Power-off USB. On some laptops such as Dell and Apple MacBook models, it is possible to plug a device in, close the laptop (putting it into sleep mode) and have the device continue to charge.[citation needed]

Q1: On what laptops are the USB ports marked with a USB symbol with an added lightening bolt icon?
A1: On Dell and Toshiba laptops
Q2: What does dell call the feature that lets USB drives to remain powered when the computer is off?
A2: PowerShare
Q3: On what laptops are the sleep-and-charge marked with a non-standard symbol?
A3: On Acer Inc. and Packard Bell laptops
The GSM Association (GSMA) followed suit on 17 February 2009, and on 22 April 2009, this was further endorsed by the CTIA – The Wireless Association, with the International Telecommunication Union (ITU) announcing on 22 October 2009 that it had also embraced the Universal Charging Solution as its "energy-efficient one-charger-fits-all new mobile phone solution," and added: "Based on the Micro-USB interface, UCS chargers will also include a 4-star or higher efficiency rating—up to three times more energy-efficient than an unrated charger."

Q1: When did the GSM Association follow suit?
A1: 17 February 2009
Q2: UCS chargers will also include what?
A2: a 4-star or higher efficiency rating
Q3: When was this further endorsed by the CTIA?
A3: 22 April 2009
In June 2009, many of the world's largest mobile phone manufacturers signed an EC-sponsored Memorandum of Understanding (MoU), agreeing to make most data-enabled mobile phones marketed in the European Union compatible with a common External Power Supply (EPS). The EU's common EPS specification (EN 62684:2010) references the USB Battery Charging standard and is similar to the GSMA/OMTP and Chinese charging solutions. In January 2011, the International Electrotechnical Commission (IEC) released its version of the (EU's) common EPS standard as IEC 62684:2011.

Q1: When did many of the largest mobile phone manufacturers sign an EC-sponsored MoU?
A1: June 2009
Q2: What did the MoU make the manufacturers agree to do?
A2: to make most data-enabled mobile phones marketed in the European Union compatible with a common External Power Supply
Q3: When did the IEC release its version of the common EPS standard as IEC 62684:2011?
A3: January 2011
Some USB devices require more power than is permitted by the specifications for a single port. This is common for external hard and optical disc drives, and generally for devices with motors or lamps. Such devices can use an external power supply, which is allowed by the standard, or use a dual-input USB cable, one input of which is used for power and data transfer, the other solely for power, which makes the device a non-standard USB device. Some USB ports and external hubs can, in practice, supply more power to USB devices than required by the specification but a standard-compliant device may not depend on this.

Q1: Some USB devices require what?
A1: more power than is permitted by the specifications for a single port.
Q2: Some devices such as an external hard and optical disk drive can use what?
A2: an external power supply
Q3: What is another alternative for power for an external hard and optical disk drive?
A3: a dual-input USB cable
Q4: What is the purpose of a dual-input USB cable?
A4: one input of which is used for power and data transfer, the other solely for power
In addition to limiting the total average power used by the device, the USB specification limits the inrush current (i.e., that used to charge decoupling and filter capacitors) when the device is first connected. Otherwise, connecting a device could cause problems with the host's internal power. USB devices are also required to automatically enter ultra low-power suspend mode when the USB host is suspended. Nevertheless, many USB host interfaces do not cut off the power supply to USB devices when they are suspended.

Q1: What does the USB specification limit?
A1: the inrush current
Q2: When is the inrush current affected by the USB specification?
A2: when the device is first connected
Q3: What are USB devices required to enter?
A3: ultra low-power suspend mode when the USB host is suspended
Q4: Many USB host interfaces do not what?
A4: cut off the power supply to USB devices when they are suspended
Some non-standard USB devices use the 5 V power supply without participating in a proper USB network, which negotiates power draw with the host interface. These are usually called USB decorations.[citation needed] Examples include USB-powered keyboard lights, fans, mug coolers and heaters, battery chargers, miniature vacuum cleaners, and even miniature lava lamps. In most cases, these items contain no digital circuitry, and thus are not standard compliant USB devices. This may cause problems with some computers, such as drawing too much current and damaging circuitry. Prior to the Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host, which then permits the device to switch into high-power mode.

Q1: What do some non-standard USB devices use?
A1: the 5 V power supply without participating in a proper USB network
Q2: What Negotiates power draw with the host interface?
A2: the 5 V power supply
Q3: What does the USB specification require prior to the Battery Charging Specification?
A3: that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host
USB data is transmitted by toggling the data lines between the J state and the opposite K state. USB encodes data using the NRZI line coding; a 0 bit is transmitted by toggling the data lines from J to K or vice versa, while a 1 bit is transmitted by leaving the data lines as-is. To ensure a minimum density of signal transitions remains in the bitstream, USB uses bit stuffing; an extra 0 bit is inserted into the data stream after any appearance of six consecutive 1 bits. Seven consecutive received 1 bits is always an error. USB 3.0 has introduced additional data transmission encodings.

Q1: How is the USB data transmitted?
A1: by toggling the data lines between the J state and the opposite K state
Q2: What does USB use to encode data?
A2: the NRZI line coding
Q3: To ensure a minimum density of signal transitions  remains in the bitsream, what does USB use?
A3: bit stuffing
A USB packet's end, called EOP (end-of-packet), is indicated by the transmitter driving 2 bit times of SE0 (D+ and D− both below max.) and 1 bit time of J state. After this, the transmitter ceases to drive the D+/D− lines and the aforementioned pull up resistors hold it in the J (idle) state. Sometimes skew due to hubs can add as much as one bit time before the SE0 of the end of packet. This extra bit can also result in a "bit stuff violation" if the six bits before it in the CRC are 1s. This bit should be ignored by receiver.

Q1: What is a USB packet's end called?
A1: EOP (end-of-packet)
Q2: What can skew due to hubs add?
A2: as much as one bit time before the SE0 of the end of packet
Q3: What can this extra bit result in?
A3: "bit stuff violation
USB 2.0 devices use a special protocol during reset, called chirping, to negotiate the high bandwidth mode with the host/hub. A device that is HS capable first connects as an FS device (D+ pulled high), but upon receiving a USB RESET (both D+ and D− driven LOW by host for 10 to 20 ms) it pulls the D− line high, known as chirp K. This indicates to the host that the device is high bandwidth. If the host/hub is also HS capable, it chirps (returns alternating J and K states on D− and D+ lines) letting the device know that the hub operates at high bandwidth. The device has to receive at least three sets of KJ chirps before it changes to high bandwidth terminations and begins high bandwidth signaling. Because USB 3.0 uses wiring separate and additional to that used by USB 2.0 and USB 1.x, such bandwidth negotiation is not required.

Q1: What type of protocol is used for USB 2.0 devices during a reset?
A1: a special protocol
Q2: What is the special protocol during a USB 2.0 device reset called?
A2: chirping
Q3:  A device that is HS capable first connects as a what?
A3: an FS device (D+ pulled high)
According to routine testing performed by CNet, write operations to typical Hi-Speed (USB 2.0) hard drives can sustain rates of 25–30 MB/s, while read operations are at 30–42 MB/s; this is 70% of the total available bus bandwidth. For USB 3.0, typical write speed is 70–90 MB/s, while read speed is 90–110 MB/s. Mask Tests, also known as Eye Diagram Tests, are used to determine the quality of a signal in the time domain. They are defined in the referenced document as part of the electrical test description for the high-speed (HS) mode at 480 Mbit/s.

Q1: Write operations to typical Hi-Speed hard drives can what?
A1: sustain rates of 25–30 MB/s,
Q2:  For USB 3.0, typical write speed is what?
A2: 70–90 MB/s
Q3: What is the read speed for USB 3.0?
A3: 90–110 MB/s
After the sync field, all packets are made of 8-bit bytes, transmitted least-significant bit first. The first byte is a packet identifier (PID) byte. The PID is actually 4 bits; the byte consists of the 4-bit PID followed by its bitwise complement. This redundancy helps detect errors. (Note also that a PID byte contains at most four consecutive 1 bits, and thus never needs bit-stuffing, even when combined with the final 1 bit in the sync byte. However, trailing 1 bits in the PID may require bit-stuffing within the first few bits of the payload.)

Q1: After the sync field, all packets are made of how many bit bytes?
A1: 8-bit bytes
Q2: How are the bit bytes transmitted?
A2: least-significant bit first
Q3: The first byte is what?
A3: a packet identifier (PID) byte
Handshake packets consist of only a single PID byte, and are generally sent in response to data packets. Error detection is provided by transmitting four bits that represent the packet type twice, in a single PID byte using complemented form. Three basic types are ACK, indicating that data was successfully received, NAK, indicating that the data cannot be received and should be retried, and STALL, indicating that the device has an error condition and cannot transfer data until some corrective action (such as device initialization) occurs.

Q1: Handshake packets consist of only a single what?
A1: PID byte
Q2: When are handshake packets generally sent?
A2: in response to data packets
Q3: What is provided by transmitting four bits that represent the packet type twice, in a single PID byte using complemented form?
A3: Error detection
IN and OUT tokens contain a seven-bit device number and four-bit function number (for multifunction devices) and command the device to transmit DATAx packets, or receive the following DATAx packets, respectively. An IN token expects a response from a device. The response may be a NAK or STALL response, or a DATAx frame. In the latter case, the host issues an ACK handshake if appropriate. An OUT token is followed immediately by a DATAx frame. The device responds with ACK, NAK, NYET, or STALL, as appropriate.

Q1: IN and OUT tokens contain what?
A1: a seven-bit device number and four-bit function number
Q2: An IN token expects what?
A2: a response from a device
Q3: An OUT token is followed immediately by a what?
A3: DATAx frame
USB 2.0 also added a larger three-byte SPLIT token with a seven-bit hub number, 12 bits of control flags, and a five-bit CRC. This is used to perform split transactions. Rather than tie up the high-bandwidth USB bus sending data to a slower USB device, the nearest high-bandwidth capable hub receives a SPLIT token followed by one or two USB packets at high bandwidth, performs the data transfer at full or low bandwidth, and provides the response at high bandwidth when prompted by a second SPLIT token.

Q1:  a larger three-byte SPLIT token with a seven-bit hub number, 12 bits of control flags, and a five-bit CRC were created to do what?
A1: to perform split transactions
Q2:  Rather than tie up the high-bandwidth USB bus sending data to a slower USB device, what happens?
A2: the nearest high-bandwidth capable hub receives a SPLIT token followed by one or two USB packets at high bandwidth
Q3: How many bits of control flags did USB 2.0 add?
A3: 12 bits
There are two basic forms of data packet, DATA0 and DATA1. A data packet must always be preceded by an address token, and is usually followed by a handshake token from the receiver back to the transmitter. The two packet types provide the 1-bit sequence number required by Stop-and-wait ARQ. If a USB host does not receive a response (such as an ACK) for data it has transmitted, it does not know if the data was received or not; the data might have been lost in transit, or it might have been received but the handshake response was lost.

Q1: There are two basic forms of data packet, what are they?
A1: DATA0 and DATA1
Q2: A data packet must always be preceded by what?
A2: an address token
Q3: What is a data packet usually followed by?
A3: a handshake token from the receiver back to the transmitter
Low-bandwidth devices are supported with a special PID value, PRE. This marks the beginning of a low-bandwidth packet, and is used by hubs that normally do not send full-bandwidth packets to low-bandwidth devices. Since all PID bytes include four 0 bits, they leave the bus in the full-bandwidth K state, which is the same as the low-bandwidth J state. It is followed by a brief pause, during which hubs enable their low-bandwidth outputs, already idling in the J state. Then a low-bandwidth packet follows, beginning with a sync sequence and PID byte, and ending with a brief period of SE0. Full-bandwidth devices other than hubs can simply ignore the PRE packet and its low-bandwidth contents, until the final SE0 indicates that a new packet follows.

Q1: Low-bandwidth devices are supported with what?
A1: a special PID value, PRE
Q2: All PID bytes include how many 0 bits?
A2: four 0 bits
Q3:  Full-bandwidth devices other than hubs can what?
A3: simply ignore the PRE packet and its low-bandwidth contents
These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, FireWire 400 is faster than USB 2.0 Hi-Bandwidth in real-use, especially in high-bandwidth use such as external hard-drives. The newer FireWire 800 standard is twice as fast as FireWire 400 and faster than USB 2.0 Hi-Bandwidth both theoretically and practically. However, Firewire's speed advantages rely on low-level techniques such as direct memory access (DMA), which in turn have created opportunities for security exploits such as the DMA attack.

Q1: These and other differences reflect the differing design goals of what?
A1: two buses
Q2: USB was designed for what?
A2: simplicity and low cost
Q3: FireWire was designed for what?
A3: high performance, particularly in time-sensitive applications such as audio and video
Q4: FireWire 400 is faster than what?
A4: USB 2.0 Hi-Bandwidth in real-use