The instruction queue is 6-bytes in length, operates on FIFO basis, and receives the instruction codes from memory.So, let us move further and understand the various instructions supported by the 8086 microprocessor. Explain the operations of instructions queue residing in BIU. A separate execution unit (EU) and bus interface unit (BIU) are provided. 11.3: CPU model for the 8086 microprocessor.
All the coprocessor instructions are ESCLC3 Assembler. Microprocessor interprets and executes the normal instruction set and the coprocessor interprets and executes only the coprocessor instructions. The microprocessor and coprocessor can execute their respective instructions simultaneously. Is a 16/32-bit complex instruction set computer (CISC) microprocessor.8087 coprocessor is designed to operate with 8086 microprocessor.
The size of the operand must be the same.The source holds either the immediate data, register or memory location. So, these instructions involve two operands i.e., the source and the destination. In data transfer group of instructions data or address can be transferred to either register, memory or I/O ports.In order to accomplish any transfer, the source and destination must be known. Data Transfer InstructionThis group includes the instructions used for moving the data from one place to another. LC-3 Overview: Instruction Set Opcodes 15 opcodes Operate instructions: ADD, AND.The instruction set in 8086 microprocessor are classified as follows:Let us now understand each type of instructions in detail.
And the result is stored in register 2.The data in the operand is added with the data in the memory location with the carry flag. Basically, the status of the result of the operations is reflected by the flag.The data in the two registers are added and output is stored in register 2.The immediate data in the operand is added with the data present in the register and the result is stored in that particular register.This instruction adds the data given in the operand with the data in the accumulator and the result is loaded in the accumulator.The data in the two registers are added along with the bit of the carry flag. Arithmetic InstructionsThese instructions are used in order to execute arithmetic instructions like addition, subtraction, multiplication, division, increment or decrement.The flags of the 8086 microprocessor are altered when arithmetic and logical instructions are executed. This stack memory is generated when SP is decremented by 2.The data present in the stack memory is transferred to either 16-bit register or memory location given in the operand and SP gets incremented by 2.It allows the exchange of data between two registers or a register to memory location.The data present in the input port is transferred to accumulator and its address is present in the DX register given in the operand.The data of the input port is moved to the accumulator whose memory address is given in the instruction.The data in the accumulator is moved to the output port whose address is specified in the DX register.The data in the accumulator is moved to the port whose address is given in the instruction.This instruction loads the register with the effective address of the memory location.The data is in the first two memory location is moved to the register and from the next two memory locations is moved to DS register.The lower byte of the data of the flag register is moved to the higher byte register of the accumulator.It moves the data in the higher byte of flag register to the lower byte flag register. While in the case of AX, 16-bit data at the accumulator is transferred.It allows the transfer of 16-bit data present in the memory or register present as an operand to the stack memory. And if the data is of 16-bit then it is transferred to the higher-order address of the accumulator.If AL is present as the operand, then 8-bit data at the accumulator is transferred to the memory.
Simply put changes the sign of the data.The data of the register or memory specified in the operand is incremented by 1.The data in the specified register or memory location is decremented by 1.The status of the flag register is modified by comparing the data of the two registers without altering the data of the registers. The AL register stores the quotient and AH register stores the remainder.This instruction generates the 2’s complement of the data present in the register or memory. So, this instruction is used for the conversion of binary data into unpacked BCD.The unsigned binary data in the accumulator is divided by the unsigned binary data in the register.
The MSB of the data shifts to carry flag and LSB becomes 0.The data byte is shifted to the right. And AL and AX store the result of the operation.Exclusive OR operation is performed by this instruction on the data present in register 1 and 2 and register 2 holds the result of the operation.This instruction performs AND operation of the data present in two registers and the output is used to modify the status of flag register.It generates a complement of data present in register or memory.The data byte of register or memory given in the operand is shifted to the left. And the accumulator stores the result.The data in register 1 is logically ORed with the data in memory and the result is stored in that memory location.The immediate data in the operand is ORed with the data in the accumulator. The outcome of the operation executed by logical instructions is represented as the status of flag register.AND operation over each bit of two registers is performed and register 2 stores the result.The immediate data is ANDed with the data present in the accumulator. Logical InstructionsThese instructions perform operations like AND, OR, complement, shift and rotate on the binary data.
These instructions do not modify the status of flag registers.This instruction transfers the control to the effective address within the segment stored in the register or memory location specified in the operand.RET transfers the control to the actual program/ procedure from the previously called procedure.The 16-bit data in the instruction is added to the data in IP.The 8-bit data is converted into 16-bit and added with the data in IP.The 16-bit data present in the register or memory is added with the data in the IP and IP stores the result.
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