8085 Microprocessor Instruction Flag Impact
The 8085 microprocessor utilizes status flags (Zero, Sign, Carry, Parity, Auxiliary Carry) to indicate the result of arithmetic and logical operations. Certain instructions modify these flags, while others do not.
Instruction Flag Analysis
Let's examine the effect of each given instruction on the 8085 flags:
- $RLC$: This instruction rotates the accumulator content one bit to the left. The most significant bit is moved to the Carry flag (CY), and the least significant bit. The Carry flag (CY) is affected.
- $PUSH$: This instruction pushes the contents of a register pair onto the stack. It only modifies the Stack Pointer (SP). This operation does not affect any status flags (Zero, Sign, Carry, Parity, Auxiliary Carry).
- $ORI$: This instruction performs a logical OR operation between the accumulator and an immediate data byte. The result updates the accumulator and affects the Zero (Z), Sign (S), Parity (P), Carry (CY), and Auxiliary Carry (AC) flags.
- $INR$: This instruction increments the content of a register or memory location by one. It affects the Zero (Z), Sign (S), Parity (P), and Auxiliary Carry (AC) flags. It does not affect the Carry flag (CY).
Conclusion
Based on the analysis, the $PUSH$ instruction is the only one among the options that does not alter any of the status flags in the 8085 microprocessor.
Important Questions from Instruction Set of 8085
The technique of assigning a memory address to each I/O device in the computer system is called -
In an 8085 microprocessor, the instruction CMP B has been executed while the contents of accumulator is less than that of register B. As a result, carry flag and zero flag will be respectively -
A fetch cycle is the
Determine the contents of accumulator if the instruction RAL is executed twice. Assume the contents of accumulator is AAH and CY = 0.
Calculate the time required to execute the entire instruction cycle if two machine codes, 0011 1110 and 0011 0010, are stored in memory locations 2000H and 2001H, respectively.
If the clock frequency is 2 MHz, the first machine code represents opcode to load data byte in the accumulator and the second code represents data to be loaded in the accumulator.
