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Flag Register

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What is Flag register in 8085 microprocessor? 8085 is a second generation 8 bit microprocessor. It is the base for studying and using all the modern microprocessors available in the market .  The Flag register is nothing but a Status Register of size 8 bit.   It can carry 8 bits and only 5 of them are useful in 8085 and the  other 3 are left vacant.    ** Therefore, 8085 has five flags -  1. Sign flag (S) 2. Zero flag (Z) 3. Auxillary carry flag (AC) 4. Parity flag (P) 5. Carry flag (C) PIC : - BIT POSITIONS OF VARIOUS FLAGS IN A FLAG REGISTER OF 8085 Well. Let’s discuss all the flags in a sequential manner. 1.SIGN FLAG:  After execution of any arithmetic or logical instruction if the result of accumulator i.e. most significant bit(i.e. d7 th) is  1 then Sign Flag is set to 1 else reset to 0.   ( After execution of arithmetic and logical instruction if the result is positive then sign flag is reset and if result is neg...
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DCR

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Syntax: DCR R Where R can be any of the general purpose registers (A,B,C,D,E,H andL) Byte: 1byte Addressing Mode: Register   Addressing Working:  1.  2.  3.  4. Flag Example: DCR B   Where [B]= 10H After execution of  DCR B  [B]= 0F H
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IN

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Syntax: IN 8-bit Where  8-bit  is an output port address. Byte: 2byte Addressing Mode: Direct  Addressing Working:  1. 2.  Example: IN 35H Where [35H]= 20 H After execution of above [A] = 20H
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