MCQs on Microprocessor

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01․ Maximum of how many devices can be connected simultaneously to the microprocessor via 8257 in DMA data transfer mode?
4
6
8
10

Maximum 4 devices can be connected simultaneously to the microprocessor via 8257 in DMA data transfer mode.
02․ A microprocessor with a 12-bit address bus will be able to access
1 K bytes
4 K bytes
8 K bytes
10 K bytes

A microprocessor with a 12-bit address bus will be able to access 212 =22 × 210 = 4 K bytes
03․ The frequency of the driving network connected between pins 1 and 2 of 8085 microprocessor is
twice the desired frequency
equal to the desired frequency
four times the desired frequency
none of the above

In 8085 microprocessor the input 1 and 2 determines the clock frequency. It is generally a RC or LC type network.Two such network when working parallel gives half of their respective frequency as equivalent frequency.So the driving network connected between pin 1 and 2 must have twice of the desired frequency.
04․ A high on RESET OUT signifies that
all the registers of the CPU are being reset
all the registers and counters are being reset
all the registers and counters are being reset and this signal can be used to reset external support chip
processing can begin when this signal goes high

A high on RESET OUT signifies that all the registers and counters are being reset and this signal can be used to reset external support chip.
05․ How can we make any bit of a register “0”?
AND that bit with “0” and remaining bits with “1”.
AND that bit with “1” and remaining bits with “0”.
OR that bit with “0” and remaining bits with “1”.
OR that bit with “1” and remaining bits with “0”.

If we want to make any bit “0”, then we have to AND that bit with “0” so that the bit becomes “0”. We also have to AND the remaining bits of the register with “1” so that they remain unaltered.
06․ PSW stands for
accumulator contents
flag byte
accumulator and flag register contents
none

PSW (Processor Status Word) is a combined status of accumulator and flag register together where accumulator is the higher-order register and the flags are the low-order register.
07․ DMA is used between
microprocessor and I/O
microprocessor and memory
memory and I/O
none

DMA (Direct memory access) is a process of high speed data transfer under the control of external devices.It is used when the microprocessor controlled data transfer is too slow. DMA allows data transfer between source and destination thus bypassing the microprocessor. DMA is used between memory and I/O.
08․ Temporary registers in 8085 are
B and C.
D and E.
H and L.
W and Z.

W and Z are temporary registers which are used only by processor. These registers are used to hold 8 bit data during the execution of some instruction. They are not accessible to the users.
09․ Register pair used to indicate memory
B and C
D and E
H and L
W and Z

In microprocessor BC,DE and HL register pair can be used by the programmer.H and L register pair is used to act as memory pointer and it holds 16 bit address of memory location.
10․ Total numbers of output pins in 8085 microprocessor are
13
27
30
40

Total no. of output pins in 8085 is 27. The output pins are A8-A15(8pins), AD0-AD7(8 pins),ALE,S0,S1,IO/M, RD,WR,HLDA,INTA,RESET OUT,CLK,SOD.
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