Introductory concept

Question 1

logic levels

Answer 1

The voltage level used to represent 1s and 0s are called logic levels.

Question 2

Digital Waveform

Answer 2

Series of pulses.

Question 3

Pulse

Answer 3

It consists of leading(rise time: :10% to 90% amplitude) n trailing edge(fall time : 90% to 10% amplitude). Pulse width is between 50%s od both edges. They can be +ve going or -ve going.

Question 4

Duty Cycle

Answer 4

(Pulse width/time period)*100%

Question 5

The clock

Answer 5

in digital systems, each waveform is synchronized with a basic timing waveform CLOCK. Periodic it is.
Its time period is the time for one bit. and doesn’t carry information. During one period, information waveform is either high(1) or low(0).

Question 6

Timing diagrams

Answer 6

A graph of digital waveforms to give the time relationship between them.

Question 7

USB

Answer 7

Universal Serial Bus

Question 8

Data Transfer

Answer 8

1. Serial Transfer

2. Parallel Transfer.

Question 9

Serial Transfer

Answer 9

Pro:
Requires only One line.
Con:
Requires time proportional to the data amt.

Question 10

Parallel transfer.

Answer 10

Pro:
requires one time interval only.
Con:
Requires multiple lines.

Question 11

Logic Gate

Answer 11

A circuit which performs specified logic function (and, or).
ALU consists of many such logic gates.

Question 12

Inverter

Answer 12

The logic circuit of not function. inverting the input.

Question 13

Comparator

Answer 13

The comparison function. A logic gate that performs magnitude comparison. a box with 2 input lines (magnitude a and b ) and 3 output lines ( a>b, a<b></b>

Question 14

Adder

Answer 14

An adder

adds two binary numbers (on inputs A and B with a carry input Cin) and generates a sum and a carry output (Cout).

Question 15

Subtractor. ( logic circuit)

Answer 15

A subtracter requires three inputs: 2 numbers and a borrow input. 2 outputs :difference, borrow output.
(An adder can do this as its special case of addition)

Question 16

Multiplier

Answer 16

multiplied 2 at a time so 2 input, 1 output product(partial). The circuit can consist of adders in conjugation +some stuff.

Question 17

Division, divider.

Answer 17

Division can be performed with a series of subtractions, comparisons, and shifts, and thus it
can also be done using an adder in conjunction with other circuits.
Two inputs.
output: quotient and the remainder.

Question 18

Code conversion function.

Answer 18

conversion between binary and other codes such as the binary coded decimal (BCD) and the Gray code.

Question 19

Code

Answer 19

A code is a set of bits arranged in a unique pattern and used to represent specified information

Question 20

Encoder

Answer 20

one certain type of encoder converts each of the
decimal digits, 0 - 9, to a binary code. A HIGH level on the input ( 10 input lines for 10 chars) produces logic levels that represent the proper binary code on the
output lines.

Question 21

Decoder

Answer 21

example, displays with seven segments( when all segments lit they show 8 ). Input of binary and appropriate output lines are activated and light the proper segments to display the decimal
digit corresponding to the binary code.

Question 22

The Data Selection Function

Answer 22

Consists of Multiplexer (mux) and demultiplexer (demux).Multiplexing and demultiplexing are used when data from several sources are to be
transmitted over one line to a distant location and redistributed to several destinations.

Question 23

Mux n demux

Answer 23

a logic circuit that switches digital data from several input lines onto a single output line in a specified time sequence is mux and demux is its opposite.

Question 24

time-division multiplexing

Answer 24

during the first time interval, input A data go to output D. During the second time interval, input B data go to output E. During the third time interval, input C
data go to output F.
After this, the sequence repeats. Because the time is divided up among several sources and destinations where each has its turn to send and receive data, this process is called time-division multiplexing (TDM)

Question 25

who uses what for memory in a computer?

to retain binary data for a period of time.

Answer 25

Rom n ram n small caches: Semiconductor.
Registers: Semiconductor flip flops.
Hard drives: Optomagnetic disk

Question 26

Flip Flop

Answer 26

Bistable ( two stable states), store one bit. high output means stored 1.

Question 27

Register

Answer 27

Made of multiple flip flops to store multiple bits.
Shift registers: Shift the bits.
that can be parallelly ( ppl sitting in roller coaster) or serially ( ppl entering bus).

Question 28

Counters

Answer 28

Their basic purpose is to count events represented by changing levels or pulses. To count, the counter must “remember” the present number, hence storage req and flip flops used.

Question 29

A process control system.

Answer 29

Recall the system for bottling vitamin tablets.

Question 30

What is a programable logic device?

Answer 30

A programable logic device has an undefined function at the time of manufacture.

Question 31

Pros of PLDs and fixed-function logic?

Answer 31

PLDs:
1. Allows us to rewrite function without replacing components.
2. Faster and cheaper implementation.
3. Less board space.
Fixed Function Logic:
- to implement a small segment of logic it may more efficient to use fixed-function logic.

Question 32

Categories of Programmable logic:

Answer 32

1. Field Programmable Gate Array.
2. PLD’s
   a. Simple PLD
   b. Complex PLD.

Question 33

SPLD:

Answer 33

Generally, an SPLD can replace up to ten fixed-function ICs and their interconnections. Pins: 24-28.
Two categories:
1. Programmable Array Logic: one time programmed, has programmable array of and gates and a fixed array of or gates.
2. Generic Array Logic: reprogrammable as has a reprogrammable array of and gate + a fixed array of OR gates with programmable outputs.

Question 34

CPLD:

Answer 34

Made of multiple SPLD. Pins: 44-160.
It consists of logic array blocks (labs), programmable interconnection array (PIA). there can be from 2-64 LABs. 1 LAB almost is 1 SPLD.

Question 35

(PQFP)

Answer 35

Typical CPLD plastic quad flat packages (PQFP)

Question 36

Chip density

Answer 36

amount of circuitry that could be put on a chip.

Question 37

Field Programmable Gate Array Basic elements?

Answer 37

It has logic blocks (not as complex as LABs) (10s of 1000s) and programmable interconnection and Input/Output Blocks. and maybe memory and additional resources.
EX: FPGA ball-grid array package.

Question 38

FPGA architecture classification based on logic blocks.

Answer 38

If logic blocks are simple then FPGA architecture is called fine-grained, if larger then coarse-grained.

Question 39

FPGA input/output blocks elaboration, n programmable interconnection:

Answer 39

The I/O blocks are on the outer
edges of the structure and provide individually selectable input, output, or bidirectional
access to the outside world.
The distributed programmable interconnection matrix provides for interconnection of the logic blocks and connection to inputs and outputs.

Question 40

Microcontroller:

Answer 40

A microcontroller is basically a special-purpose small computer. Microcontrollers are
generally used for embedded system applications. An embedded system is a system that is
designed to perform one or a few dedicated functions within a larger system.

Question 41

Microcontroller, compare it with PLD.

Answer 41

The internal circuitry is fixed and its operations are determined by a program ( series of instruction ) (language C or Basic ) to perform a specific operation.
The internal circuitry of a PLD is programmed into it, and once programmed, the circuitry performs required operations.In a PLD a program determines the logic function.

Question 42

Fixed Function logic:

Answer 42

In fixed-function

logic devices, the logic functions are set by the manufacturer and cannot be altered.

Question 43

Integrated circuit (IC) packages are classified according to the way they are mounted on
printed circuit boards (PCBs) , they are:

Answer 43

through-hole mounted or surface mounted

Question 44

through-hole type packages:

Answer 44

These have pins (leads) that are inserted through holes in the PCB and can be soldered to conductors on the opposite side. EX: dual in-line package (DIP)

Question 45

Surface mounting

Answer 45

• space-saving.
• The pins of surface-mounted packages are soldered directly to conductors on one side of the board, leaving the other side free for additional circuits and these pins placed closer.
  Ex:small-outline integrated circuit (SOIC)

Question 46

SMT, SSOP

Answer 46

-leads of the SSOP (shrink small-outline package) are formed into a “gull-wing” shape.

Question 47

SMT,PLCC

Answer 47

-The leads of the PLCC (plastic-leaded chip carrier) are turned under the package in a J-type shape.

Question 48

SMT,LCC

Answer 48

-LCC (leadless ceramic chip) has metal contacts molded into its ceramic body.

Question 49

LQFP,SMT

Answer 49

-The LQFP (low-profile quad flat package) also has gull-wing leads.

Question 50

CSP, FBGA : SMT

Answer 50

-Both the CSP (chip scale package) and the FBGA (fine-pitch ball grid array) have contacts embedded in the bottom of the package.

Question 51

Pin Numbering

Answer 51

-pin 1 is indicated by an identifier that can be either a small dot, a notch, or a bevelled edge.
-On right or opp of pin 1 is the pin with the highest count.
- Starting with pin 1, the pin numbers increase as you
go down, then across and up
-The pin numbers
increase going counterclockwise as viewed from the top of the package

Question 52

Complexity Classifications for Fixed-Function ICs

Answer 52

The complexity figures stated here for SSI ( x =0, y = 10),
MSI(10,100), LSI(100,10000), VLSI(10,000-100,000), and ULSI (>100,000)
-from x to y equivalent gates on a chip. They include logic functions such as encoders, decoders,
counters, registers, multiplexers, arithmetic circuits, small memories, and others.