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MICROPROCESSOR AND MICROCONTROLLER

List out the interrupt pins provided in 8085?

The 8085 microprocessor has five interrupt inputs. They are TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR. These interrupts have a fixed priority of interrupt service. If two or more interrupts go high at the same time, the 8085 will service them on priority basis. The TRAP has the highest priority followed bye RST 7.5,RST 6.5, RST 5.5. The priority of interrupts in 8085 is shown in the table. Interrupts Priority

TRAP

RST 7.5

RST 6.5

RST 5.5

INTR

2.Name the control signals and status signals of 8085?

a)ALE b) and c)IO/ ,S0and S1

3.What is the importance of an ALU register in 8085?

ALU has two inputs .One input is supplied by the accumulator and other from temporary data register .The programmer cannot access this temporary data register .However it is internally used for execution of most of the arithmetic and logical instruction

4.what is the purpose of Instruction register in 8085 Microprocessor?

In a typical process operation the processor first fetches the opcode of instruction from memory .The CPU stores this opcode in a register called the IR. This opcode is further sent to the instruction decoder to select one of the 256 alternatives.

5.What are the functions of Data Bus and Control bus in a Microprocessor?

AD0 to AD7 :The 8 bit data bus (D0 to D7 ) is multiplexed with the lower half (A0 to A7 ) of the 16 bit address bus. During first part of the machine cycle (T1) lower 8 bits of memory address or I/O address appear on the bus. During remaining part of the machine cycle (T2 &T3) these lines are used as a bidirectional data bus We know that AD0 to AD7 lines are multiplexed and lower half (A0 to A7 ) is available only during (T1) of the machine cycle .This lower half of an address must be latched in (T1) of the machine cycle so that it is available through out the machine cycle .The latching of lower half of an address bus is done by using external latch and ALE signal from 8085.

6.How is clock signal important for the operation of a processor

8085 has a on chip clock generator .The internal clock generator requires tuned circuit like LC,R,C. The internal clock generator divides oscillator frequency by 2 and generates clock signal which can be used for synchronizing external devices.

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