Serial communication

Question 1

Bit rate

Answer 1

Unit of measurement of number of bits processed per unit time often bps or bits

Question 2

Baud rate

Answer 2

unit of measurement of sysmbol (symbol per second)

Question 3

Endianness primarily

Answer 3

describes the order in which the bits are transmitted over a communicaton channel
Big endian: MSB transmitted first
Little endian: MSB transmitted last

Question 4

full duplex

Answer 4

simultaneous data transmission and reception over one channel

Question 5

half duplex

Answer 5

uniderectional data transmission and reception over one channel (bidirectional,
not at the same time)

Question 6

Peripheral communications

Answer 6

it refers to the methods through which microprocessors interact with external devices or peripherals. It is vital for extending the capabilities of microprocessor

Question 7

how does serial communication transmits

Answer 7

one at a time, sequentially

Question 8

how does parallel communication transmits

Answer 8

Multiple bits at a time

Question 9

dicuss, data tranfer, hardware, reliabilty higher clock rate of serial portcommunication

Answer 9

▪ Data transfer: only one bit can be transmitted at a time
▪ hardware: simple hardware, fewer wires and connectors needed. More scalable
▪ Reliability: No cross talk between wires, no clock skew as there is no need to syncronise multiple lines
▪ Higher clock rate: Increased reliabilty means serial data rates can clock faster

Question 10

dicuss, data tranfer, hardware, reliabilty higher clock rate of parallel portcommunication

Answer 10

▪ Data transfer: multiple bits can be transmitted at once
▪ Hardware: more complex hardware as more wires and connectors needed
▪ Reliabilty: cross talk between different wires
▪ Higher clock rate: reduced reliability means parallel data rates are limited to lower frequencies

Question 11

Synchronous serial communication

Answer 11

A common clock is shared by the receiver and transmitter, often in the form of a seperate dedicated clock line

Question 12

Asynchronous serial communication

Answer 12

The transmitter does not need to send a clock signal. Both transmitter and receiver agree on timing parameters in advance

Question 13

Full form of UART

Answer 13

Universal asynchronous receive transmit

Question 14

UART communication do?

Answer 14

▪ Converts data from parallel to serial.
▪ Sequential data is transmitted along serial cable from Tx on sending
device to Rx on receiving device
▪ Receives sequential data and transforms it back into parallel data

Question 15

How is serial port data transmitted

Answer 15

as data packets

Question 16

what does each data packet contain

Answer 16

Each packet contains overhead bits such as start bit, stop bit(s) an optional parity bit aw well as 5 to 9 data bits

Question 17

What is parity

Answer 17

Parity is a crude form of error detection. Thers is odd parity and even parity

Question 18

Even parity

Answer 18

even parity bit will be logic high if there is an odd number of data logic high

Question 18

Odd parity

Answer 18

parity will be logic high if there is data contains an even number of logic high bits to ensure a constant odd number of logic highs

Question 19

what does each pack have ?

Answer 19

start + data + parity(optional) + stop

Question 20

Can the parity check indicate where
the error occurred? Why or why not?

Answer 20

The parity check cannot indicate where the error occurred because it only tells you that the total number of 1’s is not as expected (i.e., the parity is wrong). It gives no information about which specific bit is in error.

Question 21

What is the logic bit for start and stop bit

Answer 21

start is low logic bit
stop is high logic bit

Question 22

what is UART sampling

Answer 22

▪transmitter generates data streams
▪receiver tries to sample in middle of bit period to avoid errors due to mistranslation
▪due to lack of syncronising clock, system is system is susceptible to error

Question 23

what is majority voting

Answer 23

majority voting is a method used in asynchronous serial port communication to ensure the reliability of data transmission especially in noisy environments

Question 24

what principal does majority voting work on

Answer 24

majority voting operates on the principal of redundancy by sampling each bit multiple times at RX, the binary value that appears most often in the RX data is considered the true value of the bit

Question 25

what does majority voting do ?

Answer 25

Majority voting significantly reduces the probability of bit errors due to noise BUT introduces additional complexity and latency in communication

Question 26

Advantages of majority voting

Answer 26

▪ Noise immunity: can increase the likelihood of the correct bit value chosen in a noisy environment ▪ Improved reliability: Reduces risk of bit errors

Question 27

Disadvantages of majority voting

Answer 27

▪ Latency: Must complete ALL sampling before deciding bit value ▪ Complexity: Requires additional logic or software for voting ▪ Not foolproof: If noise dominates entire sampling, risk of error exists

Question 28

Transmit timing formula

Answer 28

Duration of single data packet is (n+3)τTX ▪ τTX is the reciprocal of the baud rate ▪ All bits sampled in the middle of bit period this can be achieved by using various methods

Question 29

How does data transmission occur

Answer 29

Data transmission normally occurs under interrupt control. This frees up the processor to perform other tasks

Question 30

What are FIFO

Answer 30

▪ FIFO Buffers are a type of hardware memory that stores data in queue fashion. ▪ FIFOs need to be big enough to not lose characters. FIFO depth is a key characteristic. ▪ Typically generated by leaving data where it is in memory and pointers are used to access the data. When pointers get to the end of the reserved area they need to wrap around.

Question 31

what is the RS232

Answer 31

▪ RS232 is a standard describing a type of serial asynchronous communication. ▪ The standard defines connector type, pin assignments, voltage levels, max bit rate, cable length etc. ▪ There are a minimum of three pins Tx, Rx, GND with other pins used for data flow control.

Question 32

what does USB stand for

Answer 32

USB – Universal Serial Bus

Question 33

what is USB used for

Answer 33

▪ USB can be used to connect one microprocessor to a number of devices, limited only by load and number of address bits – typically 127 devices ▪ It can be used to supply power to connected devices

Question 34

what is usb endpoints

Answer 34

Host reads and writes to a set of memory addresses that act as in/out baskets on each device called endpoints

Question 35

what is enumeration

Answer 35

The control point is important for enumeration which is the process whereby a connected device is detected and configured and its list of endpoints are added to those the host can access.

Question 36

USB communication

Answer 36

▪All communication initiated by the host ▪ Host controls communication timing using time intervals called frames. Time interval determined by the USB speed ▪ Each frame starts with a Start of Frame sequence ▪ Host communicates with devices during the frame – called transactions