Digital integration 2

Question 1

What does UART stand for?

Answer 1

Universal Asynchronous Receiver-Transmitter

Question 2

What does I2C stand for?

Answer 2

Inter-Integrated-Circuit

Question 3

What does SPI stand for?

Answer 3

Serial Peripheral Interface

Question 4

What does CAN-BUS stand for?

Answer 4

Controller Area Network Bus

Question 5

What area of electronics are CAN-BUSs extensively sued within?

Answer 5

Automotive electronics

Question 6

What is RS-232?

Answer 6

It is an external serial communications standard

Question 7

When was RS-232 designed?

Answer 7

1960s

Question 8

Is RS-232 an example of synchronous or asynchronous transmission?

Answer 8

Asynchronous

Question 9

What are the voltage levels for logic signals in RS-232?

Answer 9

-15 to -5 for logic 0

5 to 15 for logic 1

Question 10

How is UART similar to RS-232?

Answer 10

UART is essentially the same as RS-232 but uses generic 5v or 3.3v logic levels and can have longer frames than 8 bits

Question 11

Is I2C synchronous or asynchronous?

Answer 11

Synchronous

Question 12

What do SCL and SDA stand for in I2C?

Answer 12

Serial Clock and Serial Data

Question 13

What is meant by an open-collector bus scheme?

Answer 13

By default the bus is high and any connected device may pull them low

Question 14

When does an arbitration process commence in I2C?

Answer 14

When two devices attempt to initiate communication at the same time.

Question 15

What is clock stretching in I2C?

Answer 15

If receiving device struggles to keep up can slow down data transfer by holding clock line low.

Question 16

What are the speed rates of standard, fast mode, fast mode + and high speed mode I2C?

Answer 16

standard = 100kbits/s
fast mode = 400kbits/s
fast mode + = 1Mbit/s
high speed mode = 3.4Mbit/s

Question 17

What is the equation for max pull up resistor for I2C bus?

Answer 17

R=t/(1.2C)

Question 18

What is the equation for the min pull up resistor for I2C bus?

Answer 18

R= V supply / max Sink current
R= V/3mA

Question 19

Is UART full duplex, half duplex or simplex?

Answer 19

full duplex

Question 20

Is I2c full duplex, half duplex or simplex?

Answer 20

half duplex

Question 21

What does SPI use instead of the open-collector approach?

Answer 21

It uses tri-state push-pull digital outputs

Question 22

What are some differences between SPI and I2C?

Answer 22

SPI is generally faster.
SPI doesn’t require bi-directional level-shifters.
There can only be one master device in SPI.
No arbitration process needed in SPI.

Question 23

CAN uses open-collector differential signalling. What is this?

Answer 23

There are two conductors CAN high and CAN low. They are normally implemented as shielded twisted pair

Question 24

What is the nominal line voltage of CAN? What logic level is this regarded as?

Answer 24

2.5V

logic high

Question 25

How is a logic low transmitted in CANH and CANL?

Answer 25

CANH needs to increase by 1V and CANL needs to decrease by 1V.

Question 26

How do you avoid signals reflecting in CAN?

Answer 26

By terminating the conductors in the correct resistance

Question 27

What CAN speeds are possible at a few meters compared to up to 1km?

Answer 27

few metres = 1Mbit/s | up to 1km = 10kbits/s

Question 28

Is CAN asynchronous or synchronous?

Answer 28

Asynchronous

Question 29

When do receivers re-synchronise their clocks in CAN?

Answer 29

When a logic high is asserted.

Question 30

How many consecutive bits of the same polarity can you have in CAN?

Answer 30

No more than 5 otherwise the receivers clocks cant stay synchronised.