About this previous year paper
Microprocessor (NEC-503)
Section-Wise Important Questions & Study Notes
SECTION–A
(Attempt all questions | 2 × 10 = 20)
This section checks basic concepts, definitions, and short explanations.
Write 2–3 lines only, be precise.
1. Microprocessor & Technology Used
A microprocessor is a programmable digital device that performs arithmetic, logic, and control operations.
It is fabricated using VLSI (Very Large Scale Integration) technology.
2. Buses in a Microprocessor
Address bus: carries memory addresses Data bus: transfers data
Control bus: carries control signals like RD, WR, ALE
3. Basic Block Diagram of Microprocessor
Includes ALU, registers, control unit, buses, and clock system.
Explain function of each block briefly.
4. Address Capability of 8085 (64 KB)
8085 has a 16-bit address bus, so it can access
216=65,536 bytes =64 KB2^{16} = 65,536 \text{ bytes } = 64 \text{ KB}216=65,536 bytes =64 KB
5. Instruction Set of 8085
8085 supports 74 basic instructions (around 246 opcodes including variations).
6. Addressing Modes of 8085
Immediate, Register, Direct, Register Indirect, and Implied addressing modes.
7. Memory Segmentation in 8086
Memory is divided into segments (CS, DS, SS, ES) of 64 KB each to access 1 MB memory efficiently.
8. Hardware Interrupts in 8085
8085 supports 5 hardware interrupts: TRAP, RST 7.5, RST 6.5, RST 5.5, INTR.
9. I/O Ports in 8085
8085 can access 256 I/O ports using 8-bit port addressing.
10. Multiplexing of A0–A7 and D0–D7
To reduce pin count, lower address bus and data bus are multiplexed and separated using ALE signal.
SECTION–B
(Attempt any THREE | 10 × 3 = 30)
Answers should be descriptive and supported with neat diagrams.
1. Architecture of 8085
Draw and explain: ALU
Accumulator Registers
Instruction decoder Timing & control unit
2. Interrupts in 8085
Explain: Hardware interrupts
Software interrupts Priority order
Masking of interrupts
3. IC-8254 Timer
Draw pin diagram & block diagram.
Explain counters, control word register, and modes of operation.
4. I/O Mapped I/O vs Memory Mapped I/O
| I/O Mapped | Memory Mapped |
|---|---|
| Separate address space | Same memory space |
| Less instructions | More instructions |
| Faster | Slower |
5. Programmable Peripheral Interface (8255)
Explain block diagram and Modes 0, 1, and 2 with applications.
SECTION–C
(Attempt any ONE | 10 × 1 = 10)
3(a) 8086 Architecture Explain features and draw block diagram.
Explain functions of:
BIU (Bus Interface Unit) EU (Execution Unit)
OR
3(b) Interrupts in 8086
Explain: Hardware interrupts
Software interrupts NMI and maskable interrupts