Lecture 7

Question 1

PLC

Answer 1

Programmable Controllers - device for industrial sequential operation management such as assembly, packing etc.

Question 2

PLC Basic Symbols

Answer 2

Question 3

Transmission Gates

Answer 3

• X and C=0 — 0
• X and C=1 — X
• X or C=0 — X
• X or C=1 — 1
• X ExOR C=0 — X
• X ExOR C=1 — NOT X

Question 4

Compliment of a number

Answer 4

• compliment of 123 = 1000 - 123 = 877
• compliment of 2411 = 10,000 - 2411 = 7589
• To subtract a number, add the compliment and remove the first digit

Question 5

Two’s Compliment

Answer 5

• Inverse digits and add 1
• eg. twos compliment of 1010 = 0101 +1 = 0110

Question 6

Size of register and size of compliment number

Answer 6

• size of register determines compliment length
• eg. 4 bit: compliment of 0110 = 1010
• eg. 8 bit: compliment of 0110 = 1111 1010

Question 7

Flags

Answer 7

• Status Register
• Z = result zero (1), result not zero (0)
• N = result negative (1), result not negative (0)
• C = Carry Generated (1), carry not generated (0)
• V = Overflow (1), no overflow (0)
• Carry = if result is too large to fit in the same number of binary numbers as original numbers (work out using decimal and convert back!)
• Overflow = If the sign bit of the both operands are the same and the sign bit of the result is different

Question 8

Two forms of encoding digital info

Answer 8

NRZ and NRZI

Question 9

NRZ

Answer 9

• No return to zero.
• simplist
• difficult to keep clock when sending out long strings of 0 or 1

Question 10

NRZI

Answer 10

• No return to zero inverted
• Transmission rule:
  
  • If data bit =1, change level
  • If data bit = 0, dont change
• Advantage: ensures 1 is transmitted safely

Question 11

Successive Approxiations - Converting Analogue to digital

Answer 11

• Analogue input applied to computer
• clock used to generate binary numbers
• D to A converter translated numbers to analogue voltage and sends to computer
• If Vclock > Vin, gate closes and binary number stops increasing

Question 12

Latching

Answer 12

A circuit, which one energise,maintains that state untl another input is recieved

Question 13

Machine Leel

Answer 13

Digital code to translate assembly langage to binary

Question 14

Assembly Language

Answer 14

Primitive language that an operater uses

Question 15

Types of RAM

Answer 15

• SRAM, once the input is given, the content will remain until changed by a subsequent valid input.
• The data storage device in the DRAM bit cell is a capacitor. When a logic 1 is written to the bit cell, it charges up the capacitor until the voltage across it is also a logic 1. As the charge in the bit cell tends to drop, the memory is continuously refreshed for keeping its contents. This gives it its name of dynamic RAM.

Question 16

e differences between a microprocessor and a microcontroller

Answer 16

• A microprocessor (CPU)
  
  • complete processor contained in one or a few LSI circuits, used to build a computer.
• A microcontroller
  
  • LSI circuit containing a microprocessor, memory and I/O system.

Question 17

Difference between memory location and data register

Answer 17

• A memory location is a part of the whole memory area provided by the computer. It is for storing a program instruction, or data.
• A register in a computer is a storage, and is designed to be accessed by the processor at an even faster speed than memory.

Question 18

Status Register

Answer 18

It scans and reflects the status of the arithmetic and logic after each instruction has been executed. Flags used.