The Instruction Cycle

Question 1

What are the three subcategories of the instruction cycle?

Answer 1

Fetch
Execute
Interrupt

Question 2

Describe FETCH

Answer 2

Gets next instruction

Question 3

Describe EXECUTE

Answer 3

interpret opode and perform operation

Question 4

Describe INTERRUPT

Answer 4

When interrupt occurs, save currently running process and service interrupt.

Question 5

What is indirect cycle?

Answer 5

The use of additional memory accesses to obtain operands

Question 6

What are the 5 general steps for instruction flow

Answer 6

PC has next instruction

MAR has that address

Result at address placed on data bus and moved to MBR

Result moves to IR

PC incremented

Question 7

What does the control do in the instruction cycle?

Answer 7

It checks the IR. If the IR requires indirect addressing, then an indirect addressing cycle is performed.

Question 8

What happens for interrupt cycle?

Answer 8

Contents of PC saved
New addesses loaded to PC
Fetch continues as with normal instruction cycle