Skip to main content

Questions and Answers of 8085 Microprocessor (Part-I)

By
What is a microprocessor?
A microprocessor is a multipurpose, programmable, clock driven register and ALU based electronic device. It reads binary instructions from memory, accepts binary data as input, processes data and provides result as output.

What are the various registers in 8085?
8085 has 8-bit accumulator (A), six 8-bit general purpose registers B, C, D, E, H and L, temporary data register, W and Z registers, flag register, instruction register, 16-bit program counter (PC) and 16-bit stack pointer (SP).

What are the various flags in a flag register?
Flag register is an 8-bit register in which five of the bits carry significant information in form of flags. They are S (Sign flag), Z (Zero flag), AC (Auxiliary Carry flag), P (Parity flag) and CY (Carry flag).

What is the function of accumulator?
Accumulator is an 8-bit register which is used in arithmetic, logic, load, store and input/output operations. It is also used to store the result of arithmetic and logical operations.

What is the function of program counter?
The program counter (PC) is a 16-bit special purpose register which, at a given time, stores the address of the next instruction to be fetched. It acts as a pointer to the next instruction.

What is the function of instruction register?
The processor first fetches the opcode of the instruction from the memory and stores the opcode in instruction register. This opcode is then sent to the instruction decoder to decode it.

What are hardware interrupts in 8085?
There are five hardware interrupts in 8085. They are TRAP, RST 7.5, RST 6.5, RST 5.5, INTR.

What are addressing modes in 8085?
The different methods used to select or address the operands are called addressing modes. There are five addressing modes in 8085. They are register addressing mode, immediate addressing mode, direct addressing mode, indirect addressing mode and implied addressing mode.

What happens when HLT instruction is executed?
When HLT instruction is executed, the microprocessor enters into halt state and the buses are tristated.

What is a bus?
A bus is a group of parallel conducting lines that carries data, address and control signals. The various units in microprocessor are connected by the three sets of parallel lines called buses. The three buses are the address bus, the data bus and the control bus.
Labels:

Comments

Post a Comment

Popular posts from this blog

Logical Group Instructions (Part-VI) - RLC, RRC, RAL, RAR

By
RLC: This instruction rotates the contents of accumulator to the left by one bit. It will shift B0 to B1, B1 to B2,............B7 to B0 as well as to carry flag . Only CY flag is modified. It is a one byte instruction. Implied addressing mode is used. Before execution: After execution: Example: If A = 0101 0111 = 57H and CY = 1 RLC ; Now A = 10101110 = AEH and CY = 0. RRC: This instruction rotates the contents of accumulator to the right by one bit. It will shift B7 to B6, B6 to B5,............B0 to B7 as well as to carry flag. Only CY flag is modified. It is a one byte instruction. Implied addressing mode is used. Before execution: After execution: Example: If A = 1001 1010 = 9AH and CY = 1 RLC ; Now A = 0100 1101 = 4DH and CY = 0. RAL: This instruction rotates the contents of accumulator to the left by one bit along with the carry . It will shift B0 to B1, B1 to B2,............B7 to CY and CY to B0 . Only CY flag is modifi...
Post a Comment
Read more

Program to exchange the contents of two memory locations

By
Statement: Exchange the contents of memory locations 2000H and 2001H. Example:  Initially, (2000H) = 34H (2001H) = 20H After exchanging, (2000H) = 20H (2001H) = 34H Program 1 using direct addressing instructions: LDA 2000H               ; Get the contents of location 2000H into accumulator MOV B, A                  ; Move the contents of accumulator into register B LDA 2001H                ; Get the contents of location 2001H into accumulator STA 2000H                 ; Store the contents of accumulator into location 2000H MOV A, B                  ; Move the contents of register B into accumulator STA 2001H                 ; Store the contents of accumulator into location 2001H HLT  ...
Post a Comment
Read more

Logical Group Instructions (Part-I) - ANA and ANI

By
ANA R:  This instruction logically AND the contents of the specified register with the contents of the accumulator. Register R can be any 8-bit general purpose register like A, B, C, D, E, H and L. The result is stored in the accumulator. S (Sign flag), Z (Zero flag), P (Parity flag) are modified. CY (Carry flag) is reset and AC (Auxiliary Carry flag) is set. It is a one byte instruction. Register addressing mode is used. Example: If A = 0101 1001 = 59H and B = 0000 0011 = 03H ANA B ; This instruction will logically AND the contents of A (59H) with the contents of B (03H) and the result (01H) is stored in A. ANA M: This instruction logically AND the contents of the memory location pointed by HL register pair with the contents of the accumulator. The result is stored in the accumulator. S (Sign flag), Z (Zero flag), P (Parity flag) are modified. CY (Carry flag) is reset and AC (Auxiliary Carry flag) is set. It is a one byte instruction. Register indirect a...
Post a Comment
Read more