The different flags and their positions in flag register are shown in following fig. The flag register of 8085 microprocessor consists of 5 flags. The respective bit flags up goes to 1 when the condition for the flag has occurred. Operations performed by 8085 the alu performs the arithmetic and logical operations. When an operation is performed by alu the result is transferred on data bus and status of result will be stored in flip flops. Microprocessor is a multipurpose, programmable device that accepts digital data as input, processes it. Only a single 5 volt power supply is needed, like competing processors and unlike the share this image share link copy link. The flag register in 8085 is an 8bit register which contains 5 bit positions. Here this video is a part of microprocessor and interfacing 8085. Microprocessor and assembly language programming bca vi sem gram reoti, behind aurobindo hospital, sanwer road,i ndorem. Depending upon the value of result after any arithmetic and logical operation the flag bits become set 1 or reset 0. These flags are known as zero, sign, carry, parity and auxiliary carry. The microprocessor uses this register to sequence the execution of the instructions.
Flag register in 8085 is a one byte register used to store 5 flags. Instruction set of 8085 an instruction is a binary pattern designed inside a microprocessor to perform a specific function. Jan 07, 2009 flag register the status flags of the 8080 and 8085 are single bits which indicate the logical conditions that existed as a result of the execution of the instruction just completed. The internal architecture of 8085 includes the alu, timing and control unit, instruction register and decoder, register array, interrupt control and serial io control. Only a single 5 volt power supply is needed, like competing processors and unlike the. The 8085 microprocessor kit is a lowcost single board computer designed for selflearning the popular 8085 microprocessor. Pop c 1 point the program status word register pair in an 8085 microprocessor is realized as the pair of which of the following registers. However, in our 8085 instruction set does not provide any instruction, which explicitly uses the ac flag. Interview questions on microprocessor with detailed answers. Apr 09, 2017 8085 is a second generation 8 bit microprocessor and is the base for studying and using all the modern microprocessors available in the market. Data memory the processor always uses 16bit addresses.
Flag register of 8085 microprocessor is explained using proper example. When an arithmetic operation results in zero, z flag. Flags are flipflops that store bit 0 or 1 based on the arithmetic or logical operation performed by an arithmetic and logical unit alu. The microprocessor uses these flags to test data conditions. Prerequisite flag register in 8085 microprocessor the flag register is a special purpose register.
In 8085 microprocessor, flag register consists of 8. What are the functions of flag registers in 8086 microprocessor. Intel 8085 8bit microprocessor intel 8085 is an 8bit, nmos microprocessor. An over view of 8085, architecture of 8086 microprocessor. In 8085 microprocessor, flag register consists of 8 bits and only 5 of them are useful. For sign flag if the result of an msb operation is 1 then it is set else it is reset.
Repeat steps 5 and 7 till the value in d register become zero 9. It includes the alu, register arrays and control circuit on a single chip. The 8085 machine language the 8085 from intel is an 8bit microprocessor. It has 8bit accumulator, flag register, instruction, register, six 8bit general purpose. Mar 05, 2018 there are five flags present in 8085 microprocessor. The bit position for the flags in flag register is, 4. Before knowing about the 8085 architecture in detail, lets us briefly discuss about the basic features of 8085 processor. The 80858080aprogramming model includes six registers, one accumulator, and one flag register. Jul 31, 2015 the article shows the flag register of 8085. Explain briefly the flag register in the 8085 microprocessor.
The flag register is basically a special type of register or we can also say that they are special purpose register. Jul 14, 2017 the flag register is in an 8085 microprocessor. The combination of the flag register and the accumulator is called program status word psw and psw is the 16bit unit for stack operation. Copy it in d register for bubble sort n1 times required 4. Prerequisite registers of 8085 microprocessor the flag register is a special purpose register. The status of the result is indicated by the flag bits of the flag register. The microprocessor is a semiconductor device integrated circuit manufactured by the vlsi very large scale integration technique. Figure below shows the details of the 16 bit flag register of.
Assembler directives, simple programs, procedures, and macros. For example the zero flag zf will set if the result of execution of an instruction is zero. These five flags are of 1bit ff and are known as zero, sign, carry, parity and auxiliary carry. The 8085 microprocessor has six 8bit general purpose registers. Over view of microprocessor 8085 and its application. The reason for the difference is that some actually most instructions have multiple different formats. The result of execution of daa instruction, is affected by the status of this flag. Figure below shows the details of the 16 bit flag register of 8086 cpu. The first figure shows an 8bit register, called the flag register, adjacent to the accumulator. There are five flags present in 8085 microprocessor. It is a 40 pin c package fabricated on a single lsi chip.
Let us discuss the architecture of 8085 microprocessor in detail. Immediate addressing, register addressing,direct addressing,indirect addressing. Program counter and stack pointer accumulator and flag register program counter and flag register program counter and accumulator no, the answer is incorrect. Nov 03, 2017 flag register of 8085 microprocessor is explained using proper example. Refer to the reference manual for pinouts and details. Fundamentals of microprocessor and microcontroller unit1 prof. If they are out of order, exchange the contents of a register and memory 7.
Flag register in 8085 microprocessor geeksforgeeks. Microprocessor and interfacing pdf notes mpi notes pdf. Serial input output data using 8085 8085 microprocessor has two serial inputoutput pins that are used to readwrite one bit data to and from peripheral devices. The 8085 uses a total of 246 bit patterns to form its instruction set. When an arithmetic operation results in zero, z flag is set to 1. After an arithmetic or logical operation if the result has an even number of ones, ie. Microprocessor multiple choice questions and answersintel. The zero flag is also set if a certain register content becomes zero following an increment or decrement operation of that register. May2012 parity flag parity is defined by the number of one. The time for the back cycle of the intel 8085 a2 is 200 ns. Registers b, c, d, e, h and c and five 16bit registers sp. There is a flag register which consists of a set of flip flops, this a register is 8bit wide temporary register is also 8 bit wide.
We will also take a look at the examples where flag bits are affected. The contents of the condition flags are assembled into a pro. Lecture note on microprocessor and microcontroller theory and. Flag register of 8086 microprocessor geeksforgeeks. Tutorial on introduction to 8085 architecture and programming. It is an 8bit register which contains 5 bit positions.
Algorithm translation to 8085 operations copy register d to a add register e to a copy a to register c stop processing use conditional jump instructions clear register b increment b copy a to register c. Define the function of parity flag and zero flag in 8085. Moorthi and others published 8085 microprocessor notes find, read and cite all the research you need on researchgate. Jan 07, 2009 interfacing the 8085 a brief description of the signals between the 8085 and the outside world follows. Feb 28, 2019 but 8085 microprocessor still stores this ac information in bit position 4 of the flags register. Figure format of flag register there are total 9 flags in 8086 and the flag register is divided into two types. The contents of the designated register or memory are decremented by 1 and their result is stored at the same place. Depending upon the value of result after any arithmetic and logical operation the flag bits become set 1 or reset. Yeola page 3 architecture of intel 8085 microprocessor features of 8085 intel 8085 is an 8bit, nmos microprocessor. Lecture note on microprocessor and microcontroller theory. Sid serial input data line there is an one bit input line inside the 8085 cpu pin number 5 1 bit data. It indicates some condition produced by the execution of an instruction.
There is one flag registers which contain number of flags what is a flag. Each instruction is represented by an 8bit binary value. Instructions of various types 1byte,2byte and 3byte are explained. H and l register which of these 8bit registers of 8085 microprocessor can be paired together to make a 16bit register.
All the flags are present in an 8bit register called as status register or flags register. Flag register is the second most useful component in all the generations of microprocessor, the first o. Status or flag register in 8085 microprocessor electricalvoice. Unit1 introduction to 8086 ece department microprocessors and microcontrollers page 3. Flag register of 8085 microprocessor with example 8085. This 16 bit register deals with sequencing the execution of instruction. In this video, i have explained flag register of 8085 by following outlines. Introduction to 8085 the advanced versions consume 20% less power supply. A nice feature, singlestep running, helps students learn the. Aug 30, 2019 the combination of the flag register and the accumulator is called program status word psw and psw is the 16bit unit for stack operation. Press key home, this brings current location to 8100. All interrupts are enabled by the ei instruction and disabled by the di instruction.
Accumulator register preferred register to use in arithmetic, logic and data transfer instructions because it generates the shortest machine language code must be used in multiplication and division operations must also be used in io operations bx base register also serves as an address register. The flags are stored in the 8bit register so that the programmer can examine these flags data. The entire group of instructions that a microprocessor supports is called instruction set. Explain flag register of 8085 microprocessor ques10. The flags generally reflect the status of arithmetic or logical operations. This page of 8085 microprocessor tutorial describes 8085 microprocessor programming. But 8085 microprocessor still stores this ac information in bit position 4 of the flags register. Cmp, cpi, ana, ani, xra,xri, ora, ori 8085 microprocessor. This allows instructions following to act accordingly, such as a branch as. The registers ax, bx, cx and dx are the general purpose 16bit registers. When set flag termed as set is in position 1 and in 0 position it is termed as reset. Figure format of flag register there are total 9 flags in 8086 and the flag register.
Microprocessor and interfacing notes pdf mpi pdf notes. The kit enables studying from low level programming with direct machine code entering to high level programming with pc tools easily. The content of register sp is decremented pch h pcl l the content of register h is moved to the highorder eight bits of. It is a 16 bit register with each bit corresponding to a flipflop. Flag register of 8085 microprocessor with example 8085 auxiliary.