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Q-Which of the following is a 2-word instruction set in 8085 microprocessor?
a) LDA 2500H
b) MOV A, B
c) IN 01H
d) JMP 2085H
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Answer: c
Explanation: LDA 2500H and JMP 2085H are 3-word instructions. MOV A, B is a 1-word instruction. IN 01H is a 2-word instruction, the first byte specifies the opcode and the second byte specifies the operand.
Q-Which of the following interfacing IC is a DMA controller in 8085 microprocessor?
a) 8257/37
b) 8155
c) 8253/54
d) 8279
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Answer: a
Explanation: 8155 is a multipurpose programmable I/O device. 8253/54 is a programmable counter. 8279 is a keyboard/display controller and 8257/37 is a DMA controller.
Q-Conditional instructions are independent of which of the following flag?
a) Z
b) AC
c) CY
d) P
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Answer: b
Explanation: Conditional instructions are the branching instructions in 8085 microprocessor. In this group, the program control is transferred from one location to other conditionally. They depend on the status of flags affected for previous ALU operations accept the AC flag.
Q-Suppose registers ‘A’ and ‘B’ in 8085 microprocessor contain 50H and 40H respectively. After instruction MOV A, B, what will be the contents of registers A and B?
a) 40H, 40H
b) 50H, 40H
c) 50H, 50H
d) 60H, 40H
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Answer: a
Explanation: Initially, register A contains 50H & B contains 40H. Instruction MOV A, B means move the content of B to A. So, after this operation, both registers A & B will contain 40H.
Q-How many address lines are required to connect a 4 KB RAM to a microprocessor?
a) 10
b) 16
c) 12
d) 20
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Answer: c
Explanation: 4 KB RAM is equal to 4096 × 8 bits. Total number locations are (4096 × 8)/8 = 4096 and 4096 = 212. So, 12 address lines are required to connect a 4 KB RAM to a microprocessor.
Q-Which of the following is true about stack pointer?
a) Stack pointer contains the address of the top of the stack memory
b) Stack pointer is an 8-bit register in the microprocessor
c) Stack pointer stores data permanently
d) Stack pointer is initialized after stack operation
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Answer: a
Explanation: Stack pointer is initialized before stack operation, it is a 16-bit register that stores data temporarily. It follows LIFO operation. So, it contains the address of the top of the stack memory.
Q-If a 90 GB memory has to be connected to a microprocessor, minimum how many address lines are required?
a) 36
b) 39
c) 32
d) 37
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Answer: d
Explanation: 90 GB is greater than 64 GB and less than 128 GB. For 64 GB (236 Bytes), a minimum of 36 address lines are needed. So, for 90 GB, we need 36 + 1 = 37 address lines.
Q-Which addressing mode is used by 8085 microprocessor for array and list operations?
a) Base-Register
b) Direst
c) Indexed
d) Immediate
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Explanation: Indexed addressing mode is used for array and list operations in 8085 microprocessor. It uses a constant value and index register to execute the instruction.
a) 8 KB
b) 2 MB
c) 16 MB
d) 64 KB
Explanation: Total number of locations of the memory possible for 20 address lines is 220 and every location has 16/8 = 2 bytes. So, total memory capacity will be 220 × 2 = 2 MB.