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What is auxiliary carry flag in microprocessor?
Auxiliary Carry Flag (AF) is one of the six status flags in the 8086 microprocessor. This flag is used in BCD (Binary-coded Decimal) operations. The status of this flag is updated for every arithmetic or logical operation performed by ALU.
What is auxiliary flag in assembly language?
The Auxiliary flag is set (to 1) if during an “add” operation there is a carry from the low nibble (lowest four bits) to the high nibble (upper four bits), or a borrow from the high nibble to the low nibble, in the low-order 8-bit portion, during a subtraction.
What is the difference between carry and auxiliary carry flag?
The auxiliary carry flag AF watches for a 4-bit (nibble) carry, while the common carry flag CF watches for a carry-out from the MSB of the operand size.
What is the difference between carry flag and auxiliary carry flag?
What is difference between carry and auxiliary carry flag?
How many flags do microprocessor 8085 have?
In 8085 microprocessor, the flags register can have a total of eight flags. Thus a flag can be represented by 1 bit of information.
How do you determine the carrying flag?
The carry flag is set if the addition of two numbers causes a carry out of the most significant (leftmost) bits added. 2. The carry (borrow) flag is also set if the subtraction of two numbers requires a borrow into the most significant (leftmost) bits subtracted.
Why auxiliary carry flag is set to 0 in 8085?
It is said that the subtraction is performed in 2’s complement in 8085 and so the flags must be set according to the operation. However,in the figure shown, i am unable to figure out the reason behind auxiliary carry flag being set to ‘0’ and the same goes for carry flag.
What is flag register in 8085 microprocessor?
Prerequisite – Registers of 8085 microprocessor The Flag register is a Special Purpose Register. Depending upon the value of result after any arithmetic and logical operation the flag bits become set (1) or reset (0). In 8085 microprocessor, flag register consists of 8 bits and only 5 of them are useful.
How to set auxiliary carry flag to 1?
These set of instructions will set the auxiliary carry flag to 1, as on adding 2B and 39, addition of lower order nibbles B and 9 will generate a carry. Parity Flag (P) – If after any arithmetic or logical operation the result has even parity, an even number of 1 bits, the parity register becomes set i.e. 1, otherwise it becomes reset i.e. 0.
Why auxiliary carry (AC) flag is used for logical operations?
The Auxiliary Carry (AC) flag is used only for BCD operations where it represents the presence or absence of carry from the 4th bit to 5th bit. But no proper proofs are available to back as to why the flag is affected for Logical operations.
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