Quiz 4

Question 1

What is the difference between asynchronous and synchronous clocking?

Answer 1

Synchronous - synchronized by external clock

Asynchronous - synchronized by special signals along the transmission medium.

Question 2

What are some advantages and disadvantages of synchronous clocking?

Answer 2

Advantages: Lower overhead => greater throughput.

Disadvantages: Slightly more complex; Hardware is more expensive.

Question 3

What are some advantages and disadvantages of asynchronous clocking?

Answer 3

Advantages:

• Simple - doesn’t require synchronization of both communication sides
• Cheap - requires less hardware; well-suited for applications where messages are generated at irregular intervals (e.g. data entry from the keyboard) and the speed depends on different applications.

Disadvantages:
* Large relative overhead - a high proportion of the transmitted bits are uniquely for control purposes and thus carry no useful information

Question 4

What can affect the performance of an asynchronous system?

Answer 4

A bad clock. Standard used is quartz-crystal oscillator due to precision of timing.

Extra information: Frequency of resonance once rock is trimmed accurately keeps time.

Question 5

Asynchronous can only transfer ___ number of ___.

Answer 5

fixed, bits

Question 6

The start bit in an asynchronously-timed clock ….

Answer 6

doesn’t carry any information

Question 7

JTAG stands for

Answer 7

Joint Test Action Group

Question 8

JTAG can have ___ or ___ pins

Answer 8

4, 5

Question 9

What are the different pins that can come on JTAG? Which one(s) is/are optional?

Answer 9

TDI, TDO, TCK, TMS, TRST

TRST is optional

Question 10

TDI

Answer 10

Test Data In; goes into shift register

Question 11

TDO

Answer 11

Test Data Out; leaves shift register

Question 12

TCK

Answer 12

Test clock; connected to input of shift register

Question 13

TMS

Answer 13

Test Mode Select; connected to output of shift register

Question 14

In a JTAG, the device under test is wired through I/O lines into the _______

Answer 14

shift register

Question 15

The device under test in a JTAG is usually a

Answer 15

chip on a board we want to test

Question 16

SPI

Answer 16

Serial Peripheral Interface

Question 17

Is SPI synchronous or asynchronous?

Answer 17

synchronous

Question 18

What is the SPI’s data rate?

Answer 18

data rate is variable

Question 19

What is an alternate name/acronym for SPI?

Answer 19

SSI - Synchronous Serial Interface

Question 20

TRST

Answer 20

Test Reset; optional connector on JTAG

Question 21

MOSI

Answer 21

master output, slave input: logic signal on SPI bus

Question 22

MISO

Answer 22

master input, slave output: logic signal on SPI bus

Question 23

What are some possible slave devices for SPI?

Answer 23

clock/calendar, potentiometer, memory

Question 24

How many master / slave devices can work with SPI?

Answer 24

One master device, one or more slave devices.

Question 25

I2C

Answer 25

Inter-Integrated Circuit

Question 26

What is the I2C?

Answer 26

Multimaster serial single-ended computer bus

Question 27

What is the max number of devices for I2C?

Answer 27

128

Question 28

SDA

Answer 28

Serial data

Question 29

SCL

Answer 29

Serial clock line

Question 30

Acknowledge logic signals on I2C

Answer 30

1: Master wants to send info to slave 0: Master wants to receive info from slave Slave does not initiate communication

Question 31

In which direction can data flow on I2C?

Answer 31

From master to slave or slave to master

Question 32

Address always comes from ____ in I2C exchange

Answer 32

master

Question 33

How fast is I2C?

Answer 33

100 to 400kb/s

Question 34

How many bits of data does I2C support?

Answer 34

8

Question 35

The vast majority of RS-232 setups are

Answer 35

asynchronous

Question 36

Voltage of RS-232

Answer 36

Old systems used +/- 12V, now use 0V for low, 5V for high

Question 37

Types of parity

Answer 37

Even, odd, mark, space, none

Question 38

Even parity

Answer 38

If already even number of 1's - 0 | If odd number of 1's - 1

Question 39

Odd parity

Answer 39

If even number of 1's - 1 | If odd number of 1's - 0

Question 40

Mark parity

Answer 40

Always 1

Question 41

Space parity

Answer 41

Always 0

Question 42

Why is parity bit useful?

Answer 42

Good for error-checking bits

Question 43

RS-232 Data Signals

Answer 43

"Space" Logic 0 (HIGH) = +12 | "Mark" Logic 1 (LOW) = -12

Question 44

Data size for RS-232

Answer 44

5, 6, 7, or 8 bits | 5, 6, 7 use a bit old; modern systems typically use 8

Question 45

Baud vs bits/sec

Answer 45

baud rate is a measure of how many times per second a signal changes (or could change). bps is simply the number of bits transmitted per second.

Question 46

What are the two connector options for RS-232?

Answer 46

9pin and 25pin

Question 47

DTE

Answer 47

data terminal equipment

Question 48

DCE

Answer 48

data communications equipment

Question 49

RS-232C Control Signals

Answer 49

RTS, CTS, DCD, DSR, DTR, RI, +/-12V

Question 50

RTS

Answer 50

request to send: DTE tells DCE to receive data

Question 51

CTS

Answer 51

clear to send: DCE says ready to receive

Question 52

DCD

Answer 52

data carrier detect: DCE detects a carrier

Question 53

DSR

Answer 53

data set ready: DCE tells DTE it is on and ready

Question 54

DTR

Answer 54

data terminal ready: DTE tells DCE it is on; if inactive all other signals ignored

Question 55

RI

Answer 55

ring indicator: DCE tells DTE a ring has occurred

Question 56

+12V

Answer 56

Logic 1 (RS-232C Control Signal)

Question 57

-12V

Answer 57

Logic 0 (RS-232C Control Signal)