Deck 20: Control Unit Operation

Question 1

The execution of a program consists of the sequential execution of instructions.

Answer 1

True

Question 2

Each phase of the instruction cycle can be decomposed into a sequence of elementary micro-operations.

Answer 2

True

Question 3

The _________ is connected to the address lines of the system bus.

A)MBR
B)MAR
C)PC
D)IR

Answer 3

B

Question 4

For the control unit to perform its function it must have inputs that allow it to determine the state of the system and outputs that allow it to control the behavior of the system.

Question 5

Knowing the machine instruction set does not play a part in knowing the functions that the processor must perform.

Question 6

The _________ cycle occurs at the beginning of each instruction cycle and causes an instruction to be fetched from memory.

A)execute
B)indirect
C)fetch
D)interrupt

Question 7

At the completion of the execute cycle a test is made to determine whether any enabled interrupts have occurred,and if they have,the interrupt cycle occurs.

Question 8

The sequence of instruction cycles are always the same as the written sequence of instructions that make up the program.

Question 9

One technique for implementing a control unit is referred to as hardwired implementation,in which the control unit is essentially a state machine circuit.

Question 10

Each micro-operation of the fetch cycle involves the movement of data into or out of a register.

Question 11

The execute cycle is simple and predictable.

Question 12

__________ are the functional,or atomic,operations of a processor.

A)Micro-operations
B)Interrupts
C)Subcycles
D)All of the above

Question 13

The use of common data paths simplifies the interconnection layout and the control of the processor.

Question 14

The control unit is the engine that runs the entire computer.

Question 15

The "read word from memory" and "increment PC" actions cannot be used simultaneously because they will interfere with each other.

Question 16

The control unit controls the internal flow of data.

Question 17

A single micro-operation generally involves which of the following?

A)a transfer between registers
B)a transfer between a register and an external bus
C)a transfer between a register and the ALU
D)all of the above

Question 18

The number of machine cycles for an instruction depends on the number of times the processor must communicate with internal devices.

Question 19

A cycle is made up of a sequence of micro-operations.

Question 20

Each instruction executed during an instruction cycle is made up of shorter ______.

A)executions
B)subcycles
C)steps
D)none of the above

Question 21

The __________ module handles multiple levels of interrupt signals.

A)interrupt control
B)incrementer address latch
C)serial I / O control
D)decrementer address latch

Question 22

The groupings of micro-operations must follow which rule?

A)a sequence of events does not need to be followed
B)use read to and write from the same register in one time unit
C)conflicts must be avoided
D)all of the above

Question 23

The ________ pulse signals the start of each machine cycle from the control unit and alerts external circuits.

A)AC
B)INSTR
C)ALE
D)OUT

Question 24

The prefix __________ refers to the fact that each step is very simple and accomplishes very little.

Question 25

The _______ designates the state of the processor in terms of which portion of the cycle it is in.

A)ICC
B)BSA
C)ALE
D)ISC

Question 26

The ________ holds the address of the next instruction to be fetched.

A)IR
B)PC
C)MAR
D)MBR

Question 27

The ________ is connected to the data lines of the system bus.

A)MAR
B)PC
C)MBR
D)IR

Question 28

Each of the smaller cycles involves a series of steps,each of which involves the processor registers,referred to as _________.

Question 29

__________ is when the control unit examines the opcode and generates a sequence of micro-operations based on the value of the opcode.

Question 30

The ____________ generated by the control unit cause the opening and closing of logic gates,resulting in the transfer of data to and from registers and the operation of the ALU.

Question 31

The ____________ of a processor causes the processor to step through a series of micro-operations in the proper sequence,based on the program being executed.

Question 32

If the instruction specifies an indirect address,then a(n)________ cycle must precede the execute cycle.

Question 33

The six things needed to specify the function of a processor are: operations (opcodes),addressing modes,registers,I / O module interface,memory module interface,and ________.

Question 34

Which of the following is an Intel 8085 external signal?

A)CLK(OUT)
B)read control
C)HOLDA
D)all of the above

Question 35

The __________ register contains the value to be stored in memory or the last value read from memory.

Question 36

The ________ portion of the control unit issues a repetitive sequence of pulses.

A)instruction register
B)flag
C)control bus signals
D)clock

Question 37

The __________ register specifies the address in memory for a read or write operation.

Question 38

The _________ holds the last instruction fetched.

A)PC
B)MBR
C)MAR
D)IR

Question 39

Machine cycles are defined to be equivalent to ________ accesses.

A)flag
B)bus
C)clock
D)path

Question 40

The _________ of a processor generates the control signals that cause each micro-operation to be executed.

Question 41

The timing of processor operations is synchronized by the __________ and controlled by the control unit with control signals.

Question 42

Control unit implementation techniques fall into two categories: microprogrammed implementation and ___________ implementation.

Question 43

The _____________ must control the state of the instruction cycle.

Question 44

The key control unit inputs are: clock,instruction register,control signals from control bus,and _________.

Question 45

In a __________ implementation the control unit is essentially a state machine circuit and its input logic signals are transformed into a set of output logic signals,which are the control signals.