ARM

1. What is Microprocessor?

Microprocessor is a CPU fabricated on a single chip program controlled device, which fetched the instructions from memory, decodes and execute the instructions.

2. What is Microcontroller?

A microcontroller is a small computer on a single metal-oxide-semiconductor (MOS) integrated circuit (IC) chip.

3. What are the basic units of microprocessor?

The basic units or block of microprocessor are ALU, an Array of Registers and control unit.

4. Give example for 32/16/8 bit instruction set.

• 32 bit ARM instruction set

• 16 bit Thumb instruction set

• 8 bit Jazelle instruction set

5. What Is Software And Hardware?

The software is set of instruction or commands needed for performing a specific task by programmable device or a computing machine. The hardware refers to the component or device used to form computing machine in which software can be run and tested. Without software hardware is idle machine.

6. Distinguish Between Microprocessor And Microcontroller?

The microprocessor is a digital integrated circuit that can be programmed with a series of instructions to perform a specified function on data. The microcontroller is tiny little computer on single integrated circuit, which has memory, input-output on chip itself. So we can say microprocessor can perform few functions but microcontroller can perform many functions.

7. What Is An Instruction?

An instruction is an order given to a computer processor by a computer program.

8. What Is Clock Cycle?

The speed of computer processor is determined by clock cycle, which is amount of time between two pulses of an oscillator.

9. What Is Instruction Cycle?

The sequence of operation that the processor has to carry out while executing a instruction is called instruction cycle.

10. What Is Machine Cycle?

The steps performed by computer processor for each machine language instruction received.

11. What Is Cache Memory?

Cache memory is small high speed memory. It is used for temporary storage of data & information between main memory and CPU

12. What Is Flag?

Flag is flip-flop used to store the information about the status of a processor and status of instruction executed most recently.

13. What Is Instruction Set?

The set of instructions that the microprocessor can execute.

14. Why address bus is Uni-Directional?

The address is identification number used by the microprocessor to identify or access a memory location or IO device. It is an output signal from the processor. Hence the address bus is unidirectional.

15. What is Thumb in ARM?

ARM and Thumb are two different instruction sets supported by ARM cores with a “T” in their name. For instance, ARM7 TDMI supports Thumb mode. ARM instructions are 32 bits wide, and Thumb instructions are 16 wide. Thumb mode allows for code to be smaller, and can potentially be faster if the target has slow memory.

16. What is pipelining?

The process of fetching the next instruction while the current instruction is executed is called pipelining.

17. What is SPSR in ARM?

A Saved Program Status Register (SPSR) stores the current value of the CPSR when an exception is taken so that the CPSR can be restored after handling the exception.

18. What is CPSR in ARM?

The Current Program Status Register (CPSR) holds processor status and control information.

19. What is AMBA?

Arm Advanced Microcontroller Bus Architecture (AMBA) protocols are an open standard, on-chip interconnect specification for the connection and management of functional blocks in a System on Chip.

20. What is the need for cache memory?

Cache memory is the fastest system memory, required to keep up with the CPU as it fetches and executes instructions.

21. What is an interrupt in ARM?

An Interrupt, as the name suggests, interrupts the microcontroller from whatever it is doing and draws its attention to perform a special task.

22. What is Exception in ARM?

An exception is an event that occurs during the execution of a program that disrupts the normal flow of instructions.

23. What is privileged mode in ARM?

privileged mode is a computer system mode in which all instructions such as privileged instructions can be performed by the processor.

24. Why FIQ is faster than IRQ in ARM OR what is the difference between FIQ and IRQ?

FIQ has higher priority than IRQ. This means that when the core takes an FIQ exception, it automatically masks out IRQs. An IRQ cannot interrupt the FIQ handler.

25. What is the use of R13 SP?

R13 is traditionally used as the stack pointer and stores the head of the stack in the current processor mode.

26. What is the use of R14 LR register?

R14 is the link register and is where the core puts the return address whenever it calls a subroutine.

27. What is the use of R15 PC register?

The program counter is used by the CPU to point to the address of the next instruction to be executed.

28. What are the types of CORTEX-M series ?

ARMv6-M , ARMv7-M , ARMv7E-M , ARMv8-M, ARMv8.1-M

29. write RISC design philosophy.

• single cycle execution for all instruction.

• single word standard length of all instruction.

• small number of instructions.

• small number of instruction formats.

• small number of addressing modes.

• it must have hard-wired control unit.

• memory access possible by load and store instructions only.

29. write ARM design philosophy.

• Design small processor so as to have low power consumption as required for an embaded system.

• programs are made of highly dense code so as to cater the limited memory and physical size constraints.

• use slow and low cost memory, so as to reduce the overall system cost.

• implementing more peripherals on smaller die so as to reduce the cost of the chip manufacturing as well as the chip size.

30. what is core ?

Core of a microcontroller is the main part in it that performs the ALU, control unit and register sections along with the buses.

31. ARM processor support seven operating mode.

1. ABORT

2. FIQ

3. IRQ

4. SUPERVISOR

5. UNDEFINED

6. SYSTEM

7. USER

NOTE : all the modes is privileged mode except user mode. user mode is non-privileged mode.

32. what is the full form of AHB and APB?

AHB or ASB stands for Advanced high performance bus or Advanced system bus and APB stands for advanced peripheral bus.

33. how many shifts ARM contains?

ARM has two types of shift. 1) Logical shift and 2)Arithmetic shift. Logical shift is used for unsigned operands and Arithmetic shift is used for signed operand.

LSR (Logical shift right)

LSL (Logical shift left)

ASR (Arithmetic shift right)

ROR (Rotate right)

RRX (Rotate right though carry)

No rotate left in ARM.

34. What is packed and unpacked BCD?

In unpacked BCD, the lower four bits of the number represent the BCD number and the rest of the bits are zero.

E.X 0000 1001

In packed BCD, a single byte has two BCD numbers in it, one in the lower 4 bits and one in the upper 4 bits.

E.X 0101 1001

35. What is Bus-cycle time?

To access a device such as memory or I/O , the CPU provides a fixed amount of time called a bus-cycle time.

36. What is Bus-Bandwidth?

The rate of data transfer is generally called bus bandwidth.

37. What is stack?

The stack is a section of ram used by the CPU to store information temporary.

38. What is ARM?

ARM stands for advanced RISC machine. It is the family of reduced instruction set computing architectures for computer processor.

39. what is IDE ?

An IDE is a toolkit to write and execute a program.

40. what is compiler ?

It is used to convert the c program into the machine language.

41. What is linker ?

It is responsible for linking the different functions in a program.

42. What is loader?

The binary file generated by the compiler is loaded by the loader.

43. Time delay calculation of instructions.

• MOV Instruction cycle = 1

• SUB Instruction cycle = 1

• Branch Instruction cycle = 3

• ADD Instruction cycle = 1

• NOP Instruction cycle = 1

• BHI Instruction cycle = 3/1

• BLO Instruction cycle = 3/1

• BNE Instruction cycle = 3/1

• EQE Instruction cycle = 0

44. What is the use of sign extend ?

The sign extend hardware converts signed 8 bit and 16 bit numbers to 32 bit values.

45. What is the features of ARM?

• RISC architecture

• 32 bit general purpose processor

• High performance, small size

• load/store architecture

• 3-address instruction

• simple addressing modes

46. What is banked register ?

ARM register set shows all 37 registers of those 20 registers are hidden from a program at different times. These registers are called banked register.

47. What is Big-Endian byte order ?

The most significant byte of the data is placed at the byte with the lowest address. The rest of the data is placed in order in order in the next three bytes in memory.

48. What is Little-Endian byte order ?

The least significant byte of the data is placed at the byte with the lowest address. The rest of the data is placed in order in the next three bytes in memory.

49. What is the operation of BIC ?

BIC stands for BIT CLEAR. operation performed by BIC is R1 AND NOT (R2)

50. What is the operation of MVN?

MVN stands for move negated. operation performed by MVN is R0 = NOT(R1)

51. What is the use of EQU directive?

This is used to define a constant value or a fixed address.

52. What is the use for RN directive?

This is used to define a name for a register.

53. What is the use of space directive?

Using the space directive we can allocate memory for variables.

54. What is the use of ALIGN directive?

This is used to make sure data is aligned in 32-bit word or 16-bit half - word memory address.

55. Which are the types of Exception handling in ARM?

• Normal interrupt

• Fast interrupt

• Memory interrupt

• Undefined instruction

• software interrupt

56. What is the difference between Von-Neuman memory organization and Harvard memory organization ?

Von Neumann memory organization states that "Every memory location has a unique address, while the Harvard's

memory organization states that "There can be multiple memory locations with same address but different function".

57. What is the difference between RISC and CISC ?

One of the major differences between RISC and CISC is that RISC emphasizes efficiency in cycles per instruction and CISC emphasizes efficiency in instructions per program.

58. What is the use of TST instruction ?

The test instruction is used to test the contents of register to see if any bit is set to high.

The operation performed by TST is Rn AND OP2

59. What is the use of TEQ instruction ?

The test equate instruction is used to see if the contents of two registers are equal.

The operation performed by TEQ is Rn EX-OR OP2

60. What is pointer aliasing?

Two or more pointers pointing to the same location is called as the pointer aliasing.