Describe Different Types Of Instruction.

Describe different types of instruction.

 

Instruction available in a processor may be broadly classified into six groups. This are__

   (i) Data transfer instruction.

   (ii) Arithmetic instructions.

   (iii) Logical instructions.

   (iv) Program control instructions.

   (v) System control instructions.

   (iv) Input/output  (I/O) instructions.

(i) Data transfer instruction:  Data transfer instructions are concerned primarily with data transfers between the processor and main memory. Typically an ideal instruction set must be able to handle the following transfers:

       Register to Register

       Register to Memory

       Memory to Resister

       Memory to Memory

(ii) Arithmetic instructions: All instructions sets typically include ADD and SUBTRACT instructions.

Example: LEA Z, A2; Load the address of Z into the address register A2.

(iii) Logical instructions: Invariably, the instruction set of all contemporary processors include instructions to perform Boolean AND, OR, NOT and Exclusive-OR operations on a bit-by-bit basis.

Example: LSR.W#3,D5- This instruction performs a left logical shift of the low-order, 16 bits of the data register D5 by three places.

(iv) Program control instruction: In a conventional computer, instructions are always executed in the same order they are presented. Instructions that perform this are called program control instructions.

This instruction may be classified into four groups:

        >Unconditional branch instruction.

        >Conditional branch instruction.

        >Subroutine calls instructions.

        >Interrupt handling instructions.

Example: MOV AB X, R7; Move the address of X register into R7.

(v) System control instructions: With the advent of law cost VLSI microprocessors, designing systems with several processors is feasible. Such a multiprocessor system has significant advantage , such as high processing speed and more reliability.

Example:      LOOP1               TAS                        TEST

                                                BNE                        LOOP1

                                                CLR.B                     TEST

(vi)  Input/output  (I/O) instructions: Input/output  (I/O) instructions allow a processor to perform input and output operations. An input instruction allows a peripheral to transfer a word to either a CPU register to memory. Similarly, an output instruction enables a processor to transfer a word into the buffer register of a peripheral device.

Example: IN, OUT.