1.2 Logical Operations

Question 1

Draw truth tables for AND, OR, NOT, XOR, NAND and NOR

Question 2

Draw truth tables for logical expressions (e.g. A AND B (B NOR C))

Question 3

Explain the purpose of masking, the logical operation and design the mask required for a given situation

Answer 3

The purpose of masking is to identify the value of a bit

e.g. to find out the value of the leftmost bit in 10001100

i would AND it by 10000000

if the output for the leftmost bit is 1, the value is 1

Question 4

Explain how XOR could be used to encrypt and decrypt data using an encryption/decryption key

Answer 4

XOR is used to create an encrypted value with a key and an original value

original: 10000000
Key: 10000000 XOR
—————————-
Encrypted value: 00000000

the data can only be decrypted by people who have access to the key

encrypted value: 00000000
Key: 10000000 XOR
—————————————
Original: 10000000

Question 5

solve boolean identities using e.g. de morgans law etc.

Question 6

how do you clear the contents of a register

Answer 6

you AND the register with 00000000