Consider the following 1) Sign flag 2) Trap flag 3) Parity flag 4) Auxiliary carry flag. Which one o

Question

Consider the following 1) Sign flag 2) Trap flag 3) Parity flag 4) Auxiliary carry flag. Which one of the above flags is/are present in 8085 microprocessor?

Examoogle · Accepted Answer

1, 3 & 4

Explanation: The 8085 microprocessor features a 8-bit flag register containing five status flags: Sign (S), Zero (Z), Auxiliary Carry (AC), Parity (P), and Carry (CY). Among the listed options, the Sign, Parity, and Auxiliary Carry flags are part of this set, while the Trap flag is an interrupt control signal rather than a condition flag. Working Principle: The Flag Register (F) is an internal register that acts as a status indicator for the ALU. Each bit in this register is modified based on the outcome of arithmetic or logical operations: the Sign flag reflects the MSB of the result, the Parity flag indicates the number of set bits, and the Auxiliary Carry indicates a carry from bit 3 to bit 4. The 'Trap' is a non-maskable hardware interrupt, which is handled by the interrupt control unit, not the status flag register. Key Formulas: $CY \rightarrow$ Carry Flag (Bit 0); $P \rightarrow$ Parity Flag (Bit 2); $AC \rightarrow$ Auxiliary Carry Flag (Bit 4); $Z \rightarrow$ Zero Flag (Bit 6); $S \rightarrow$ Sign Flag (Bit 7) Key Points: The 8085 Flag Register is 8 bits wide, but only 5 bits are utilized.; The TRAP is the highest priority hardware interrupt in the 8085.; The status flags are updated automatically after every ALU operation.; The 'X' bits in the flag register (D1, D3, D5) are not used. Advantages: Status flags enable efficient conditional branching.; Allows real-time monitoring of ALU arithmetic status. Disadvantages: Limited flag bits constrain complex status reporting.; Non-maskable interrupts like TRAP require separate dedicated circuitry. Applications: Arithmetic logic operations (ADD, SUB, INR).; Conditional program flow control (JZ, JNC, JPE). Additional Info: Trap flag is commonly found in CPUs like x86 for debugging (single-stepping), but 8085 treats TRAP strictly as an interrupt pin.. Option B is incorrect because while Sign is a flag, Trap is not a flag in 8085. Answer: D is correct — The Sign flag, Parity flag, and Auxiliary Carry flag are standard status flags in the 8085 architecture, whereas Trap is an interrupt. Exam Tip: Always distinguish between interrupt signals (like TRAP, RST 7.5) and internal processor status flags; status flags only indicate the result of a previous operation.

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