Flag/Status Registers in Computer Architecture

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Questions and Answers

What is the purpose of the flags in the flag register?

To hold the opcode of an instruction
To store the program counter value
To indicate the result of arithmetic and logical operations (correct)
To hold the intermediate results of arithmetic operations

What is the function of the Carry flag?

To indicate the sign of the result
To handle the carry or borrow from one word to another (correct)
To indicate the parity of the result
To indicate the zero result

What type of microprocessor is 8085?

Stack-based microprocessor
Register-based microprocessor
Memory-based microprocessor
Accumulator-based microprocessor (correct)

When data is read from an input port, where is it first moved?

Accumulator (D) Signup and view all the answers

What is the number of flip-flops in a flag register?

5 (C) Signup and view all the answers

What is the purpose of the Auxiliary Carry flag?

To indicate the carry from the lower nibble to the higher nibble (A) Signup and view all the answers

What is the primary function of the Temporary Register (W and Z)?

To hold data temporarily during program execution (C) Signup and view all the answers

What is the function of the flag register?

To indicate the status of different states (A) Signup and view all the answers

What is the purpose of the accumulator register?

To perform arithmetic and logic operations (A) Signup and view all the answers

What happens to data when it is sent to an output port?

It must be first placed in the accumulator (D) Signup and view all the answers

What is the purpose of the Parity flag?

To indicate the parity of the result (D) Signup and view all the answers

What is the significance of the Zero flag?

It indicates the zero result (D) Signup and view all the answers

What is the size of the Temporary Register (W and Z)?

8-bit (B) Signup and view all the answers

How can the flags be used in decision making?

By using conditional jump instructions (C) Signup and view all the answers

During an arithmetic and logic operation, what is the role of the Temporary Register (W and Z)?

To hold the operand temporarily (C) Signup and view all the answers

Who has access to the Temporary Register (W and Z)?

Neither the programmer nor the control unit (B) Signup and view all the answers

What is the primary function of general purpose registers?

To hold or store data temporarily during program execution (D) Signup and view all the answers

How many general purpose registers are available in the 8085 microprocessor?

6 (A) Signup and view all the answers

What is the purpose of register pairs in the 8085 microprocessor?

To store 16-bit data (C) Signup and view all the answers

What is true about the general purpose registers in the 8085 microprocessor?

They can be reprogrammed by the user (D) Signup and view all the answers

What type of data can be stored in a single general purpose register in the 8085 microprocessor?

8-bit only (A) Signup and view all the answers

What is the advantage of using general purpose registers?

Easier programming (B) Signup and view all the answers

What operation can be performed directly on the registers in the 8085 microprocessor?

Data transfer operation (C) Signup and view all the answers

What is the role of the general purpose registers in a program?

To hold or store data temporarily during program execution (C) Signup and view all the answers

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Study Notes

Flag/Status Registers

A register consisting of five flip-flops, each holding the status of different states separately, is known as a flag register.
Each flip-flop is called a flag.
The flags include Sign (S), Zero (Z), Auxiliary Carry (AC), Parity (P), and Carry (CY).
The state of flags indicates the result of arithmetic and logical operations, which can be used for decision-making processes.

Carry Flag

The Carry flag is set to 1 if the last operation generates a carry; otherwise, it's 0.
This flag handles the carry or borrow from one word to another.
The Carry flag is used to store 8-bit data and perform arithmetic and logic operations.

Accumulator

The accumulator is a special-purpose register used to store 8-bit data and perform arithmetic and logic operations.
The accumulator is used when data is read from an input port or sent to an output port.

Temporary Register (W and Z)

The temporary registers W and Z are 8-bit operand registers not accessible to the programmer.
During program execution, the 8085A places data into these registers for a brief period.
These registers are used by the control unit during arithmetic and logic operations.

General Purpose Registers

General-purpose registers are used to hold or store data, results of arithmetic and logical operations, and addresses of data memory temporarily during program execution.
These registers are available to the user and can be reprogrammed by the user.
The 8085 microprocessor has six 8-bit general-purpose registers: B, C, D, E, H, and L.
These registers can be used individually to store 8-bit and 16-bit data with register pairs.
The valid pairs in 8085 microprocessor registers are BC, DE, and HL.
Data can be directly added or transferred from one register to another.