Unit 1 Flashcards
(15 cards)
What are micro-operations in computer architecture?
Micro-operations are operations performed on data stored in registers. They form the basic building blocks of computer operations.
What are the types of micro-operations?
1.Arithmetic Micro-Operations: Perform arithmetic operations on numeric data.
2.Logic Micro-Operations: Perform bit-by-bit manipulation on non-numeric data.
3.Shift Micro-Operations: Perform shift operations (left/right) on data.
4.Register Transfer Micro-Operations: Transfer binary information between registers.
What is Register Transfer Language (RTL)?
The symbolic notation used to describe micro-operation transfers among registers. Example: R2 ← R1.
What is Bus Transfer in computer architecture?
A bus is a group of wires used for transferring data between different components of a computer, such as registers and memory.
Bus transfer is the process of transferring information from one register to another through a bus.
What are the read and write operations in memory transfer?
Read Operation: Transfer from memory register (M) to Memory Buffer Register (MBR): MBR ← M
Write Operation: Transfer from MBR to memory register (M): M ← MBR
What are the basic arithmetic micro-operations and their functions?
Add Micro-Operation: R3 ← R1 + R2 (Adds contents of R1 and R2, stores in R3).
Subtract Micro-Operation: R3 ← R1 + (2’s complement of R2) (Equivalent to R1 - R2).
Increment Micro-Operation: R1 ← R1 + 1 (Increments contents of R1 by 1).
Decrement Micro-Operation: R1 ← R1 - 1 (Decrements contents of R1 by 1).
binary adder
Uses full adders connected in cascade. Each full adder takes in Augend, Addend, and Carry, producing a Sum and Carry.
What is a binary incrementer, and how is it constructed?
A binary incrementer adds one to a number in a register. It can be constructed using half adder circuits connected in cascade.
How does a 4-bit arithmetic circuit work and what operations can it perform?
Operations: Addition, Subtraction, Increment, Decrement, and Transfer.
Control: 4 full adders and 4 multiplexers controlled by S1 S0 and Cin.
Addition: D=A+B
Subtraction: D = A + B̅+1
Increment:D=A+1
Decrement: D=A−1
Transfer: D=A (When Cin = 0 and S1 S0 = 10)
What are the different types of shift micro operations
1.Logical Shift: Shifts bits with 0 entering from the serial input.
shl (shift left), shr (shift right)
2.Circular Shift (Rotate): Circulates the bits around both ends.
Cil (circular shift left),
Cir (circular shift right)
3.Arithmetic Shift: Shifts signed binary numbers while maintaining the sign bit.
ashl (arithmetic shift left),
ashr (arithmetic shift right)
What is the function of an Arithmetic Logic Shift Unit (ALU) and how does the selection table
ALU: Performs arithmetic, logic, and shift micro-operations. It uses selection inputs S0 and S1 to choose the operation and outputs the result from a multiplexer. The operations include:
Arithmetic (addition, subtraction, transfer, increment, decrement)
Logic (AND, OR, XOR, NOT)
Shift (Shift right and left operations)
Selection of Operations:
When S3S2=00: The first eight operations are arithmetic operations:
Addition, Addition with carry, Subtraction with borrow, Subtraction, Transfer A, Increment A, Decrement A.
When S3S2=01: The next four operations are logic operations (AND, OR, XOR, NOT).
When S3S2=10: Shift right operation.
When S3S2=11: Shift left operation.
What are the important fields of an instruction format?
OP code field:
Specifies which type of operation is to be performed.
Address field:
Designates a memory address or a processor register where the operand is located.
Mode field:
Specifies how the operand or effective address is calculated, indicating the method used (e.g., direct, indirect addressing).
What are the inputs and outputs of the control unit?
1 .Instruction Register – Holds current opcode, determines micro-operations.
2.Flags – Indicates processor status and ALU outcomes.
3.Clock – Drives micro-operations with each pulse.
4.Control Signals from Control Bus – Provides operation signals.
Outputs:
1.Control Signals within CPU – Data movement and ALU activation.
2.Control Signals to Control Bus – Signals to memory and I/O modules.
What are the fetch cycle, indirect cycle, and execute cycle?
Fetch Cycle:
Occurs at the start of each instruction cycle to fetch the instruction.
Micro-operations:
t1: MAR ← (PC)
t2: MBR ← memory; PC ← (PC) + 1
t3: IR ← (MBR)
Indirect Cycle:
Fetches operands if the instruction has an indirect address.
Micro-operations:
t1: MAR ← (IR(address))
t2: MBR ← memory
t3: IR(address) ← (MBR(address))
Execute Cycle:
Executes the instruction (e.g., ADD R1, X).
Micro-operations:
t1: MAR ← (IR(address))
t2: MBR ← memory
t3: R1 ← (R1) + (MBR)
Instruction Cycle (ICC):
00: Fetch cycle
01: Indirect cycle
10: Execute cycle
11: Interrupt cycle
What are the types of Control Units and their key differences?
1) Hardwired Control Unit
Built using sequential logic (FSM).
Fast execution.
Changes require hardware redesign.
2) Microprogrammed Control Unit
Uses control memory to store microinstructions (firmware).
Easy to modify (just change microprogram).
Slower due to memory access time.
Costly due to control memory.
🛠 Improvement: Instruction pipelining used to enhance performance.
