4.3 ProcessorFundamentals.bit_manipulation

Question 1

What is a shift operation in computing?

Answer 1

Moving the bits stored in a register a given number of places within the register.

Question 2

What happens in a logical shift?

Answer 2

Bits shifted out of the register are replaced with zeros.

Question 3

What is an arithmetic shift?

Answer 3

A shift operation where the sign of the number is preserved.

Question 4

How does a cyclic shift work?

Answer 4

No bits are lost; bits shifted out of one end of the register are introduced at the other end.

Question 5

What is a monitor in computing?

Answer 5

A system that automatically takes readings from a device.

Question 6

What is control in computing?

Answer 6

A system that automatically takes readings from a device and uses the data to adjust the device.

Question 7

What is a mask in computing?

Answer 7

A number used with logical operators (AND, OR, XOR) to identify, remove, or set specific bits in an address or register.

Question 8

What is a binary shift?

Answer 8

Moving the bits stored in a register a given number of places within the register.

Question 9

How is shifting used in the IR (Instruction Register)?

Answer 9

Each bit in the IR may be used to identify a different interrupt.

Question 10

Example: Logical left shift of 10101111 by 3 places?

Answer 10

01111000

Question 11

Example: Arithmetic right shift of 10101111 by 3 places?

Answer 11

11110101

Question 12

What is an arithmetic shift used for?

Answer 12

Multiplication or division by powers of two.

Question 13

Example: Cyclic left shift of 10101111 by 3 places?

Answer 13

01111101

Question 14

What is a left shift?

Answer 14

Bits are shifted to the left in logical, arithmetic, and cyclic shifts.

Question 15

What is a right shift?

Answer 15

Bits are shifted to the right in logical, arithmetic, and cyclic shifts.

Question 16

What does the LSL instruction do?

Answer 16

LSL n shifts the bits in ACC logically left by n places, introducing zeros on the right.

Question 17

What does the LSR instruction do?

Answer 17

LSR n shifts the bits in ACC logically right by n places, introducing zeros on the left.

Question 18

Where are shifts always performed in assembly language?

Answer 18

On the ACC (Accumulator).

Question 19

How is bit manipulation used in monitoring and control?

Answer 19

Each bit in a register or memory location can be used as a flag to track the status of sensors or processes.

Question 20

How can a control system with eight sensors track processed data?

Answer 20

By using 8 different bits in the same memory location.

Question 21

What logical operation is used to check if a bit has been set?

Answer 21

AND

Question 22

What logical operation is used to set a bit?

Answer 22

OR

Question 23

What logical operation is used to clear a bit that has been set?

Answer 23

XOR

Question 24

What does the AND n instruction do?

Answer 24

Performs a bitwise AND operation between the contents of ACC and the operand n.

Question 25

What does the `AND

` instruction do?

Answer 25

Performs a bitwise AND operation between the contents of ACC and the contents of *

*.

Question 26

What does the `XOR n` instruction do?

Answer 26

Performs a bitwise XOR operation between the contents of ACC and the operand *n*.

Question 27

What does the `XOR

` instruction do?

Answer 27

Performs a bitwise XOR operation between the contents of ACC and the contents of *

*.

Question 28

What does the `OR

` instruction do?

Answer 28

Performs a bitwise OR operation between the contents of ACC and the contents of *

*.

Question 29

Where are the results of logical bit manipulation stored?

Answer 29

In the *ACC (Accumulator)*.

Question 30

What can `

` in bit manipulation instructions represent?

Answer 30

An absolute address or a symbolic address.

Question 31

How is the operand used in logical bit manipulation?

Answer 31

As a *mask* to set or clear bits.

Question 32

Example: Testing Sensor 3 in Assembly Language

Answer 32

**Opcode | Operand | Comment** - `LDD sensors` → Load content of *sensors* into ACC - `AND #B100` → Mask to select bit 3 only - `CMP #B100` → Check if bit 3 is set - `JPN process` → Jump to *process* routine if bit not set - `LDD sensors` → Load *sensors* into ACC - `XOR #B100` → Clear bit 3 as sensor 3 has been processed