The 8051 Microcontroller Questions

• 8051 ports and alternate functions — what is the alternate function of port pin P3.0 (labelled RXD)? Choose the correct role of P3.0 within the on-chip serial interface.
• 8051 direct addressing — does the instruction 'MOV 23H, A' copy the Accumulator to internal RAM address 23H? Decide whether this statement about direct-address destination is correct.
• 8051 reset and code fetch source — with EA held LOW at reset, where does the Program Counter fetch the first instruction from? Select the memory space the CPU uses immediately after reset when EA = 0.
• 8051 addition syntax — which statement correctly adds register R3 to the Accumulator and stores the result back in A? Choose the valid 8051 ADD form that implements A ← A + R3.
• 8051 register moves — which instruction copies the contents of the Accumulator into register R6? Select the correct MOV form that implements R6 ← A.
• 8051 subroutine control flow — does the statement 'LCALL READ' transfer execution to the line labelled READ? Judge whether LCALL followed by a label calls that subroutine and saves the return address.
• 8051 external data memory access — is data transfer to/from external RAM possible only via the MOVX instruction? Evaluate whether external data memory reads/writes require MOVX (with DPTR or @R0/@R1 as pointer).
• 8051 loop behavior — will the following code execute continuously (infinite loop)? Code at label STAT: STAT: MOV A, #01H JNZ STAT Decide whether execution remains stuck at STAT forever.
• 8051 reset input — which active-HIGH pin resets the microcontroller when driven HIGH for a proper pulse width? Select the correct pin name used to reset a standard 8051.
• ADC0804 start-of-conversion control In the ADC0804 successive-approximation ADC, which hardware input is used to initiate (start) a conversion, assuming chip select (CS) is asserted appropriately?
• 8051 memory spaces overview Is it correct that the 8051 architecture divides address space into four distinct areas: internal data, external data, internal code, and external code?
• Assembly source notation In assembly language programming, is a label primarily used to name the address (location) associated with a single line/instruction so it can be referenced elsewhere?
• 8051 register-to-accumulator move Which 8051 instruction correctly moves the contents of register R3 into the accumulator A?
• 8051 pin count and I/O allocation: “The 8051 microcontroller is a 40-pin IC, and twenty-two of these pins are used for its four 8-bit I/O ports.” Judge this claim.
• 8051 instruction set family: “Different members of the 8051 family require different instruction sets to make up for their variations.” Determine the correctness of this statement.
• 8051 reset behavior: “The RST pin of the 8051 microcontroller requires a HIGH level to generate a reset.” Decide if this statement is accurate.
• 8051 external memory capacity: “Up to 65K bytes of external code memory and 65K bytes of external data memory can be added to any 8051 family member.” Assess the statement.
• 8051 instruction “DA A” (Decimal Adjust Accumulator): “In an 8051 program, the instruction DA A adjusts the accumulator after addition so that the result becomes a valid packed BCD value.” Decide if this is correct.
• 8051 loop/counter instructions: “Writing counter or loop programs becomes much more difficult with the introduction of DJNZ and CJNE instructions.” Judge the validity of this claim. (Recovery: original text read “DJNA”; interpreted here as the standard 8051 instruction “DJNZ”.)
• 8051 interfacing context: Current-output DACs and some sensors provide an analog output as a current, which must be converted into a usable voltage for the 8051’s ADC/input stages. Is it valid to perform this current-to-voltage (I/V) conversion with a general-purpose operational amplifier configured as a transimpedance amplifier (for example, a classic 741/LM358-class op amp)?