Contents
How can set Carry flag in 8085?
Here STC stands for “SeT the Carry flag” and CMC stands for “CoMplement the Carry flag”. Note that, there isno dedicated instruction in 8085 instruction set to reset the Cy flagbit. To resent the Cy flag bit we can execute STC and CMCinstructions sequentially in this order.
Which flag is affected after execution of test instruction?
CMP and TEST instructions affect flags only and do not store a result (these instruction are used to make decisions during program execution). These instructions affect these flags only: CF, ZF, SF, OF, PF, AF.
Which instruction affects flag register?
All FLAGS registers contain the condition codes, flag bits that let the results of one machine-language instruction affect another instruction. Arithmetic and logical instructions set some or all of the flags, and conditional jump instructions take variable action based on the value of certain flags.
Which control flag is used in string instructions?
The direction flag is a flag that controls the left-to-right or right-to-left direction of string processing, stored in the FLAGS register on all x86-compatible CPUs.
What are the flags in 8085?
In 8085 microprocessor, the flags register can have a total of eight flags. Thus a flag can be represented by 1 bit of information. But only five flags are implemented in 8085….And they are:
- Carry flag (Cy),
- Auxiliary carry flag (AC),
- Sign flag (S),
- Parity flag (P), and.
- Zero flag (Z).
What is the purpose of flag register?
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.
What is the role of flag register?
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). If the MSB is 0, it indicates the number is positive and the sign flag becomes reset i.e. 0. …
Which instruction does not affect the flag in 8085?
The result of execution of DAA instruction, is affected by the status of this flag. However, in our 8085 instruction set does not provide any instruction, which explicitly uses the AC flag.
How is the flag register in the 8085 microprocessor?
In 8085 microprocessor, flag register consists of 8 bits and only 5 of them are useful. Sign Flag (S) – After any operation if the MSB (B (7)) of the result is 1, it indicates the number is negative and the sign flag becomes set, i.e. 1. If the MSB is 0, it indicates the number is positive and the sign flag becomes reset i.e. 0.
Where is the AC flag located in the 8085?
But 8085 microprocessor still stores this AC information in bit position 4 of the flags register. The result of execution of DAA instruction, is affected by the status of this flag. However, in our 8085 instruction set does not provide any instruction, which explicitly uses the AC flag.
How to control CY flag bit content in 8085?
In 8085 Instruction set,there are two instructions to control the Cy flag bit content. Thesemnemonics are STC and CMC. Both are 1-Byteinstructions.
Which is an example of an 8085 instruction?
EXAMPLE: After two numbers are added and if the sum is larger than 8 bits to be accomodated in the accumulator then it is indicated by setting the CY flag to value ‘1’. Like wise each of the flags have significance in 8085 processor.
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