Intel 8086 Microprocessor

Intel 8086 Microprocessor:

8086 Addressing Modes : We have seen how the 8086 fetches code bytes from memory by generating 20-bit physical address with the help of IP and CS. We have also seen how the 8086 accesses the stack using SS and SP. In this section we will see the different ways that an 8086 can access the data. The different ways that a processor can access data are referred to as 8086 Addressing Modes. The 8086 has 12 basic addressing modes. The various 8086 addressing modes can be classified into five groups Addressing modes for accessing immediate and register data (register and immediate modes). Addressing modes …


8086 Instruction Format : The 8086 Instruction 8086 Instruction Format vary from 1 to 6 bytes in length. Fig. 6.8 shows the instruction formats for 1 to 6 bytes instructions. As shown in the Fig. 6.8, displacements and operands may be either 8-bits or 16-bits long depending on the instruction. The opcode and the addressing mode is specified using first two bytes of an instruction. The opcode/addressing mode byte(s) may be followed by : No additional byte Two byte EA (For direct addressing only). One or two byte displacement One or two byte immediate operand One or two byte displacement followed by a one or two byte immediate …


Features of 8086 Microprocessor : The features of 8086 Microprocessor are : 1.The 8086 is a 16-bit microprocessor. The term “16-bit” means that its arithmetic logic unit, internal registers and most of its instructions are designed to work with 16-bit binary words. 2.The 8086 has a 16-bit data bus, so it can read data from or write data to memory and ports either 16 bits or 8 bits at a time. The 8088, however, has an 8-bit data bus, soil can only read data from or write data to memory and ports 8 bits at a time. 3.The 8086 has a 20-bit address bus, so …


Internal Architecture of 8086 : Fig. 6.2 shows a block diagram of Internal Architecture of 8086. It is internally divided into two separate functional units. These are the Bus Interface Unit (BIU) and the Execution Unit (EU). These two functional units can work simultaneously to increase system speed and hence the throughput. Throughput is a measure of number of instructions executed per unit time. Bus Interface Unit: The bus interface unit is the Internal Architecture of 8086 to the outside world. It provides a full 16-bit bi-directional data bus and 20-bit address bus. The bus interface unit is responsible for performing all external bus …