USB

Question 1

USB Structure (3)

Answer 1

• USB is at the top of the pyramid
• Can be connected to another hub or node
  
  • Up to 127 connected devices
• Responsible for all comms. on the bus:
  
  • Device addr
  • Bus b/w
  • Power Requirements

Question 2

Types of USB connectors (2)

Answer 2

• Plugs - ends of the cable
• Receptable - socket on the devices

Question 3

What does OTG stand for?

Answer 3

On-The-Go (type of USB)

Question 4

OTG can act as …

Answer 4

… both a host and node

Question 5

Max Cable Length of USB is limited by …

Answer 5

… the max round trip delay to allow for reflections to settle @ Tx before next bit is sent

Question 6

If USB host commands are unanswered within the allowed time …

Answer 6

… the host condsiders the command lost

Question 7

USB has evolved from a …

Answer 7

… data interface capable of supplying limited power to a primary provider of power with a data interface

Question 8

What type of signalling does USB use?

Answer 8

Differential Signalling

Question 9

What do the red lines in an Eye Diagram stand for?

Answer 9

The boundaries for performance failure

Question 10

In NRZI, bit 0 is represented by …

Answer 10

… the transition from stage J to stage K

(J + K define the differential voltage between D+ and D-)

Question 11

After 6 consecutive 1 bits …

Answer 11

… an extra 0 bit is inserted, to ensure a minimum density of signal transitions

Question 12

In NRZI, 7 conssecutive 1 bits =

Answer 12

error

Question 13

2x Mitigation of Attenuation + Distortion Techniques

Answer 13

• De-emphasis
• Equalisation

Question 14

De-emphasis Technique (2)

Answer 14

• occurs @ Tx
• ampl. of Tx signal voltage is arrnaged to be higher than normal after a logic level transition

Question 15

Equalisation Technique

Answer 15

• Occurs @ Rx
• Rx signal, R(w) is multiplied by the inverse of the channel function to recover the transmitted signal