Al register is also called accumulator because it has some characteristics different from other general purpose registers. Four registers, ax, bx, cx, and dx, are classified as data registers. Generalpurpose registers eight 32bit generalpurpose registers e. There are eight 16 bit general purpose registers on the 8086. How many types of registers are there in 8086 allinterview. Execution unit receives program instruction codes and data from biu, executes these instructions and store the result in general registers.
There are 8 general purpose registers in 8086 microprocessor. Jan, 2018 description of general data registers,segment registers and pointers and index registers of intel 8086 microprocessor and brief introduction of flags. Nonconfidential pdf versionarm dui0379h arm compiler v5. While the instructions are executed in the control unit, they may work on some. The 4 segments are code, data, extra and stack segments. Ax register is also known as accumulator register that stores operands for arithmetic operation like divided, rotate. The 8086 can access any two consecutive bytes as a word of data. Assembly language assignment help, general data registers microprocessor, general data registers given figure indicate the register organization of 8086.
These registers are basically special memory locations within the processor that have special names. General purpose registers are used to store temporary data within the microprocessor. The registers dx, cx, bx and ax are the general purpose 16bit registers. The memory in an 8086 88 based system is organized as segmented memory. The central processing unit cpu is the most important component of every computer. An x86 cpu has eight main registers in its scalar register file in 32bit mode. Lecture 3 brief history and registers of 80x86 family. In 16bit mode, such as provided by the pentium processor when operating as a virtual 8086 this is the mode used when windows 95 displays a dos prompt, the processor provides the programmer with 14 internal registers, each 16 bits wide. The 80286 microprocessor adds one major programmervisible feature to the. The sole purpose of register is to hold data for some time. General purpose registers in 8086 microprocessor geeksforgeeks. R8 r15found in the pentium 4 and core2 if 64 eflag and flag register the eflag and flag register counts for the entire 8086 and pentium microprocessor family. It is technically a volatile register, since the value isnt preserved. Apr 02, 2014 introduction to 8086 microprocessor 1.
For example, in 8bit microprocessors, the data is 8 bit whereas the address is 16 bit. All of these have various special uses, but of them, the eighth, esp, has the most special status as the stack pointer. It also has four 16bit pointers and index registers. Block diagram of intel 8086 the 8086 cpu is divided into two independent functional units. However the operand and the address information may not be of the same size. General purpose registers normally used for storing temporary results each of the registers is 16 bits wide ax, bx. Layout of the intel 80386 generalpurpose microprocessor. Once the operation is over, it stores the result in a register. Ax, bx, cx and dx registers have 2 8bit registers to access the high and low byte data registers.
The b0, b1, b2, and b3 stand for banks and each bank contains eight general purpose registers ranging from r0 to r7. General purpose registers in 8086 microprocessor read online for free. Introduction to 8086 8088 microprocesser general facilities biu and eu data registers segment registers index registers pointer registers flag register memory addressing physical memory address calculations. Microprocessor 8086 functional units tutorialspoint. The 8086 organizes memory as individual bytes of data. General purpose registers in 8086 microprocessor central. It can read or write data to a memoryport either 16bits or 8 bit at a time 8086 has a 20bit address bus which means, it can address upto 2 20 1mb memory location frequency range of 8086 is 610 mhz. Intel 8086 family users manual october 1979 author. Register organization of 8086 microprocessor the 8086 has a powerful set of registers. The register bx is used as offset storage for forming physical address in case of certain addressing modes. In computer system architecture, registers are temporary storage unit to store or hold and transfer data or instruction. General purpose registers in 8086 microprocessor tutorialspoint.
The data registers can be used as general purpose registers in some instructions. The 8086 machine contains of four 16bit data registers that are accessible on a byte or 16bit basis. Microprocessors use registers to perform their operations. Generalpurpose microprocessors page 2 of figure 2. The complete physically available memory may be divided into a number of logical segments. Introduction of registers of 8086 microprocessor youtube.
May 11, 2006 segment registers hold the base address of where a particular segment begins in memory. Jun 26, 2014 registers in 8086 microprocessor all the registers of 8086 are 16bit registers. The special purpose registers information technology essay. Eu execution unit execution unit gives instructions to biu stating from where to fetch the data and then decode and execute those instructions. These registers may be 8163264128bit depending on its use. It is of 16 bits and is divided into two 8bit registers ah and al to also perform 8bit instructions. Thus, for example, a pentium can run 8086, 80386 and 80486 code. There is the code segment cs, data segment ds, stack segment ss, and extra segment es. The general purpose registers can be used as either 8bit registers or 16bit registers. Instead operands as well as addresses are stored at the time of program execution. General purpose registers of 8086 these registers can be used as 8bit registers individually or can be used as 16bit in pair to have ax, bx, cx, and dx. The use of generalpurpose registers is to store temporary data.
The 8086 microprocessor has a 16 bit register for flag register. First, a register is a flip flop circuit in electronics language which temporarily holds data. Block diagram of intel 8086 features of 8086 microprocessor. Since the processor accesses register more quickly than memory. General purpose registers gpr are not used for storing any specific type of information. The high byte of ax is called ah and the low byte is al. There are two types of registers in register set of 8086 microprocessor,they are 1 general purpose registers and 2special purpose registers. Although these registers are general purpose, every one has its own special purpose. It includes general purpose registers, segment registers, pointers and index registers and flag register. This register has 9 flags which are divided into two parts that are as follows. A register is a storage element that can be store bits of information, a register file is a collection of registers, which are the same length. A cpu has several highspeed storage units known as registers. Name the general purpose registers available in 8086.
These data registers are accessible as either the full 16bit register, represented with the x suffix, the low byte of the full 16bit register, designated with an l suffix, or the high byte of the 16bit register. Eight of the registers are known as general purpose registers i. The 8086 also called iapx 86 is a 16bit microprocessor chip designed by intel between early 1976 and june 8, 1978, when it was released. Its alu, internal registers works with 16bit binary word 8086 has a 16bit data bus. The register set of 8086 can be categorized into 4 different groups. Explain the function of general purpose register of 8086. General data registersmicroprocessor, assembly language. The register cx is used default counter in case of string and loop instructions.
Segment registers are 16bit registers which are assumed to be holding a 20 bit number, because it is assumed you will add a zero to the end. It is generally used for arithmetical and logical instructions but in 8086 microprocessor it is not mandatory to have accumulator as the destination operand. The reverse works, however, as the 16 bit general purpose registers of the 8086 and 8088 can be used as pairs of 8 bit registers. The general purpose registers are those which may appear as operands of the arithmetic, logical, and related instructions. Fifteen general purpose registers are visible at any one time, depending. General purpose registers the four general purpose registers are the ax, bx, cx, and dx registers. There are some registers that also serve as general purpose registers. So, you can use this bx register as a something like a pointer ok. X86 assemblyx86 architecture wikibooks, open books for an. Aside from the four segment registers introduced in the previous section, the 8086 has seven general purpose registers, and two status registers. Dx register is a general purpose register which may be used as an implicit operand or destination in case of a few instructions. General purpose registers with the exception of armv6m and armv7m based processors, there are 30 or 32 if security extensions are implemented general purpose 32bit registers, that include the banked sp and lr registers. General purpose registers are used for temporary storage of data and memory access.
The intel 8088, released july 1, 1979, is a slightly modified chip with an external 8bit data bus allowing the use of cheaper and fewer supporting ics, and is notable as the processor used in the original ibm pc design. Accessing parts of registers the top portion of the programming model contains the general purpose registers. The general purpose registers are used to store temporary data in the time of different operations in microprocessor. Generalpurpose register an overview sciencedirect topics. The general purpose registers are divided into two categories. Microprocessors 6 microprocessor is a controlling unit of a microcomputer, fabricated on a small chip capable of performing alu arithmetic logical unit operations and communicating with the other.