(SEM IV) THEORY EXAMINATION 2021-22 MICROPROCESSOR

SECTION–A — Short Questions, but Conceptual and Theory-Dense (20 Marks)

Section–A contains ten short questions, each carrying two marks, but despite being labelled as “brief,” each question touches upon a core conceptual area of microprocessor fundamentals. The questions are designed to check whether the student has a strong foundation on topics such as the evolution of microprocessors, the types of microprocessors, and the register organization within a microprocessor. For example, the first question asks about the evolution of microprocessors, which requires an understanding of how microprocessors developed from simple 4-bit and 8-bit processors to modern multi-core architectures. Another question asks about types of microprocessors, which covers categories like CISC, RISC, DSP processors, and microcontrollers.

The section then moves into more specific components of the microprocessor. You are asked about interrupts, which requires explaining how external or internal events can alter the normal flow of a program. The Bus Interface Unit (BIU) question tests your knowledge of how the 8086 fetches instructions and addresses memory. You must also understand what an instruction set is, as well as the role of assembly language in programming hardware-level instructions. The purpose of branch operations appears in another question, testing your understanding of how control flows inside a program. Finally, Section–A ends with questions on peripheral devices and the DMA controller, requiring you to explain how microprocessors interact with external hardware and how Direct Memory Access improves system efficiency. Altogether, this section checks your fundamental theoretical understanding across the entire microprocessor domain.
 

SECTION–B — Long, Descriptive, Deep-Understanding Questions (30 Marks)

Section–B requires the student to attempt any three out of five 10-mark questions. These questions are designed to test a deeper understanding of architecture, control, instructions, and interfacing concepts. For instance, one question focuses entirely on the 8253 programmable counter, asking for a complete explanation of its modes, internal structure, and usage. This requires knowledge of how timers and counters support frequency division, event counting, and waveform generation in embedded systems.

Another question delves into machine control and assembler directives, requiring you to explain directives like ORG, EQU, DB, DW, along with machine control operations like HLT, WAIT, NOP, and LOCK. You are also asked to provide a complete description of hardware and software interrupts, which means explaining the interrupt vector table, priority, masking, and how hardware triggers differ from software-triggered interrupts.

There is also a question on conditional call and return instructions, which demands clarity on how control is transferred depending on flag status (e.g., CALL NZ, CALL Z, RET P, RET C). Additionally, you may choose a detailed explanation of microprocessor architecture, which includes describing functional components like ALU, registers, buses, control unit, timing and control, and execution flow. Section–B expects structured answers, diagrams where necessary, and precise explanations that demonstrate both conceptual and practical understanding.

SECTION–C — Technical Application-Based Questions (10 Marks Each)

Section–C is divided into multiple parts, and from each subsection (Q3 to Q7), you must attempt any one question. These questions are specific, technical, and require detailed diagrams and explanations.

In Section 3, one option asks for short notes on the 8259 Programmable Interrupt Controller and the 8251 USART, both of which are essential interfacing chips used in real-time and serial communication systems. The alternate question asks you to explain the Execution Unit and Memory Segmentation of the microprocessor, requiring a thorough understanding of how 8086 divides memory into segments and how the EU functions separately from the BIU.
 

In Section 4, one question asks for the internal block diagram of the programmable timer (likely 8253/8254) and requires explanation of its modes of operation. The alternate question requires explaining the architecture of the 8086 microprocessor with a neat diagram, covering modules like EU, BIU, registers, ALU, etc.
(Reference: Page 2 Q4(a), Q4(b)) 

In Section 5, the focus shifts to addressing techniques and DMA. One option asks for detailed descriptions of the different addressing modes of 8086 with examples (like immediate, direct, register, based, indexed, based-indexed). The alternate asks you to discuss the internal block diagram of the 8237 DMA controller and its operating modes, requiring a deeper understanding of how DMA bypasses CPU for faster data transfer.
(Reference: Page 2 Q5(a), Q5(b)) 

In Section 6, the first question requires drawing the block diagram of the 8255 Programmable Peripheral Interface (PPI) and explaining its ports and control word register. The alternate option deals with data transfer schemes and interfacing devices, covering programmed I/O, interrupt-driven I/O, DMA, and peripheral communication.
(Reference: Page 2 Q6(a), Q6(b)) 

Finally, Section 7 focuses on programming and memory. One option asks for a detailed note on Assembler Level Programs (ASMs) and Memory Space, which requires discussing low-level programming, assembler flow, and how memory is structured in microprocessor-based systems. The alternate question involves instruction formats and a numerical design problem where you calculate how many memory chips of size 2048×1 are needed to build a 128 KB memory — a test of both theory and practical design understanding.
(Reference: Page 2 Q7(a), Q7(b)) 

FINAL SUMMARY (In Full Paragraph)

This Microprocessor exam paper is designed to evaluate both theoretical understanding and practical skills. Section–A ensures you know foundational terms and building blocks of microprocessors. Section–B expects descriptive, structured answers involving architecture, counters, interrupts, and assembler directives. Section–C pushes deeper into interfacing chips, control circuits, memory architecture, instruction formats, DMA controllers, and detailed block diagrams. The structure of the paper encourages a balance of conceptual clarity, diagram accuracy, and problem-solving ability, reflecting the real-world complexity of microprocessor-based systems.