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You Are On Multi Choice Question Bank SET 989

49451. Which of the following commands will move the value at port 3 to register 2?





49452. The number of data registers is:





49453. When the 8051 is reset and the EA line is LOW, the program counter points to the first program instruction in the:





49454. The designs of a centigrade thermometer and a PWM speed-control circuit can be implemented by the 8051.



49455. What is the difference between the 8031 and the 8051?





49456. The I/O port that does not have a dual-purpose role is:





49457. To interface external EPROM memory for applications, it is necessary to demultiplex the address/data lines of the 8051.



49458. The following command will copy the accumulator to the location whose address is 23H: MOV 23H,A



49459. The special function registers can be referred to by their hex addresses or by their register names.



49460. The contents of the accumulator after this operation MOV A,#2BH ORL A,00H will be:





49461. The following program will cause the 8051 to be stuck in a loop: LOOP: MOV A, #00H  JNZ LOOP



49462. Which of the following commands will copy the contents of RAM whose address is in register 0 to port 1?





49463. The statement LCALL READ passes control to the line labelled READ.



49464. Which of the following commands will copy the contents of location 4H to the accumulator?





49465. The microcontroller is useful in systems that have nonvariable programs for dedicated applications.



49466. The total amount of external code memory that can be interfaced to the 8051 is:





49467. The ADC0804 has ________ resolution.





49468. A HIGH on which pin resets the 8051 microcontroller?





49469. An alternate function of port pin P3.1 in the 8051 is:





49470. Which of the following instructions will move the contents of the accumulator to register 6?





49471. The following command will rotate the 8 bits of the accumulator one position to the left: RL A



49472. An alternate function of port pin P3.0 (RXD) in the 8051 is:





49473. Analog output current must be converted into a usable voltage. To perform this current-to-voltage conversion a 700 op amp may be used.



49474. A Celsius thermometer is an application for the 8051 microcontroller.



49475. The RST pin requires a HIGH to reset the 8051 microcontroller.



49476. A microcontroller is called a computer on a chip.



49477. In an 8051 program DA A adjusts the value in the accumulator resulting from an addition into two BCDs.



49478. Different instruction sets must make up for the various members of the 8051 family.



49479. The ADC 0804 is an analog-to-digital converter that provides 8-bit output resolution that can be directly interfaced to a microcontroller.



49480. Writing counter/loop programs is much more difficult with the introduction of the DJNA and the CJNE instructions.



49481. The 8051 is a 40-pin IC. Twenty-two pins are needed for the four I/O ports.



49482. Up to 65K of code memory and 65K of data memory can be added to any of the 8051 family members.



49483. The internal RAM memory of the 8051 is:





49484. This program code will be executed continuously: STAT: MOV A, #01H  JNZ STAT



49485. The 8051 has ________ 16-bit counter/timers.





49486. The address space of the 8051 is divided into four distinct areas: internal data, external data, internal code, and external code.



49487. Data transfer from I/O to external data memory can only be done with the MOVX command.



49488. If the rms current through a 4.7 k resistor is 4 mA, the peak voltage drop across the resistor is





49489. A pulse waveform has a high time of 8 ms and a pulse width of 32 ms. The duty cycle is





49490. A 20 kHz pulse waveform consists of pulses that are 15 s wide. The duty cycle





49491. If the peak of a sine wave is 13 V, the peak-to-peak value is





49492. A sinusoidal current has an rms value of 14 mA. The peak-to-peak value is





49493. A signal with a 400 s period has a frequency of





49494. A sine wave of 15 kHz is changing at a faster rate than a sine wave with a frequency of





49495. The average value of a 12 V peak sine wave over one complete cycle is





49496. When a sine wave has a frequency of 100 Hz in 12 s it goes through





49497. A sawtooth wave has a period of 10 ms. Its frequency is





49498. Two series resistors are connected to an ac source. If there are 7.5 V rms across one resistor and 4.2 V rms across the other, the peak source voltage is





49499. If a sine wave goes through 10 cycles in 20 s, the period is





49500. A square wave has a period of 60 s. The first odd harmonic is





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