Data-Path and Control Unit MCQ Quiz - Objective Question with Answer for Data-Path and Control Unit - Download Free PDF

Extended Binary Coded Decimal Interchange Code is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems.

The correct answer is 2) allows easy implementation of new instructions.

Key Points

• A microprogrammed control unit allows easy implementation of new instructions.
  • Microprogramming involves storing control information in a memory called control memory.
  • When a new instruction is needed, it can be added to the control memory without changing the hardware.
  • This makes the control unit highly flexible and adaptable to new instructions or changes in instruction set architecture.
  • Unlike a hardwired control unit, which requires physical changes to the wiring and circuitry, a microprogrammed control unit only requires updates to the control memory.

Additional Information

• Microprogrammed control units are typically used in complex instruction set computers (CISC) due to their ability to handle complex instructions efficiently.
• They provide a systematic and organized approach to control unit design.
• However, microprogrammed control units are generally slower than hardwired control units because of the additional memory access time required to fetch microinstructions.
• Despite being slower, their flexibility and ease of updating make them suitable for many applications.

The correct answer is stack frame.

Key Points

• A stack frame is a data structure that contains information about the function or procedure invocation.
  • It includes the return address, which is the point to which control should return after the function completes.
  • The stack frame also contains parameters passed to the function, local variables, and other important data for the function execution.
  • Each function call creates a new stack frame, which is pushed onto the call stack.
  • When the function completes, its stack frame is popped from the stack, and control returns to the return address.
  • Managing stack frames is crucial for maintaining the correct flow of control and data during program execution.

Additional Information

• The stack base is the starting point of the stack memory region, not specific to an individual function call.
• The stack limit refers to the maximum allowed size of the stack memory region.
• The term stack record is less commonly used but can be synonymous with stack frame in some contexts.
• Understanding stack frames is important for debugging and performance optimization in software development.

The correct answer is 22

Explanation:

Step 1: Understand the Horizontal and Vertical Approaches

Horizontal Microprogramming:

• Each control signal in a group is represented by one bit in the control word.
• For n control signals in total, the control word length is the sum of all control signals.

Vertical Microprogramming:

• Each group of mutually exclusive control signals is encoded as a binary code, so the number of bits required for each group is:

 
                            \(\text{Bits required} = \lceil \log_2(\text{number of signals in the group}) \rceil\)
 

Step 2: Given Data

Step 3: Calculate Total Control Word Length for Each Approach

Horizontal Approach: In the horizontal approach, each control signal has its own bit. Thus, the total number of bits required is:

                       \(\text{Total bits} = 1 + 5 + 7 + 15 + 8 = 36\)

Vertical Approach: In the vertical approach, each group is encoded in binary. The number of bits required for each group is:

                       \(\text{Bits per group} = \lceil \log_2(\text{number of control signals in the group}) \rceil\)

For each group:

• \(G_1: \lceil \log_2(1) \rceil = 0\) (only one signal, so no bits needed)
• \(G_2: \lceil \log_2(5) \rceil = 3\)
• \(G_3: \lceil \log_2(7) \rceil = 3\)
• \(G_4: \lceil \log_2(15) \rceil = 4\)
• \(G_5: \lceil \log_2(8) \rceil = 3\)

The total number of bits required is:

                     \(\text{Total bits} = 0 + 3 + 3 + 4 + 3 = 13\)

Step 4: Bits Saved
The number of bits saved is:

                    \(\text{Bits saved} = \text{Horizontal bits} - \text{Vertical bits} = 36 - 13 = 22\)

Final Answer: 1) 22

• PCI (Peripheral Component Interconnect Express): This bus offers the lowest latency among the options. It's designed for high data rates and minimal delay, making it suitable for various devices like graphics cards, network cards, and storage.
• USB (Universal Serial Bus): A popular bus for connecting various devices, USB has higher latency compared to PCIe but remains acceptable for many applications. USB 3.0 even offers similar latency to PCIe 2.0.
• SPI (Serial Peripheral Interface): This is a low-cost bus ideal for low data rate devices. However, SPI's latency is higher than PCIe or USB.
• I2C (Inter-Integrated Circuit): Designed for chip-to-chip communication, I2C is a low-speed bus with the highest latency among the choices.:
• For the lowest latency, PCI is the clear winner. If cost is a major concern, USB or SPI might be better options.

SRAM (static RAM) is random access memory (RAM) that retains data bits in its memory as long as power is being supplied.

Inside a dynamic RAM chip, each memory cell holds one bit of information and is made up of two parts: a transistor and a capacitor.

Central Processing Unit (CPU) consists of the following features:

• CPU is considered the brain of the computer.
• CPU performs all types of data processing operations.
• It stores data, intermediate results, and instructions (program).
• It controls the operation of all parts of the computer.

Additional Information

• Memory unit:-
  • It is the amount of data that can be stored in the storage unit.
  • This storage capacity is expressed in terms of Bytes.
• Input Unit:-
  • This unit contains devices with the help of which we enter data into the computer.
  • This unit creates a link between the user and the computer.
  • They translate the information into a form understandable by the computer.
• Output unit:-
  • It consists of devices with the help of which we get the information from the computer.
  • This unit is a link between the computer and the users.
  • They translate the computer's output into a form understandable by the users.

Extended Binary Coded Decimal Interchange Code is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems.

Accumulator:

It is a register used for storing intermediate results of larger computation. It keeps track of result of any arithmetic or logic operation.

Stack pointer:

It is a register that stores the address of the last program request in a stack. It gives the address of the top of the stack. When a value is pushed into stack the processor gets the value in stack pointer, then processor decrements the address to point to the next available slot in memory and store its address in stack pointer.

Program counter:

It is a register in a computer processor that contains the address of the instruction to be executed next. It is a digital counter needed for faster execution of tasks. It is also known as instruction counter, instruction pointer, instruction address register. 

Therefore option 4 is correct.

Typically, in a microprocessor, the units in at least one of the datapaths would be: instruction registers, decode latch, ALU registers, load-store unit, writeback unit, and the memory.

To perform any operation in the CPU, data follows a specific path within the CPU to execute the instruction. 

Additional Information

System Bus:

A bus is a set of wires. The elements of the computer are linked to the buses. It can transfer data from one element to another, the source element outputs data onto the bus. The destination element then inputs this information from the bus. As the complexity of a computer system improves, it becomes more effective (in methods of minimizing connections) at using buses instead of a direct connection between each pair of devices.

ALU:

An arithmetic logic unit (ALU) is a digital circuit used to perform arithmetic and logic operations. It represents the fundamental building block of the central processing unit (CPU) of a computer. Modern CPUs contain very powerful and complex ALUs. In addition to ALUs, modern CPUs contain a control unit (CU).

• Micro program is basically a microcode to program a microprocessor.
• It is a low-level language typically consists of machine language instructions that are stored in ROM.It is a sequence of micro-instructions.
• Therefore Micro program is a set of microinstructions that define the individual operations in response to machine-language instruction.

Symbolic microprogram

• It is convenient for writing microprograms so that people can read and understand.
• The symbolic microprogram must be translated to binary so that processor can understand.
• Each symbolic microinstruction is divided into five fields: label, microoperations, CD, BR, and AD

Binary microprogram

• The binary microprogram listed in the word content of the control memory.
• When a ROM is used for the control memory, the microprogram binary list provides the truth table for fabricating the unit. Example: 000, 001, 010 etc

Important Point

Microprogramming is a Process of writing microcode for a microprocessor.

Microcode is low-level code that defines how a microprocessor should function when it executes

Serial ATA (SATA, abbreviated from Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives.

The correct answer is option 3.

Concept:

Memory chips are integrated circuits that can hold information. Memory chips are now available in a variety of RAM formats, including DRAM, EPROM, EEPROM, and SRAM. Memory chips can also be included in hardware devices such as video cards.

Explanation:

A chip having 150 gates will be classified as LSI (large-scale integration).

Large-scale integration (LSI) is the process of integrating or embedding thousands of transistors on a single silicon semiconductor microchip.

Hence the correct answer is LSI.

The correct answer is option 3.

Concept:

A control signal is represented by a pulse or frequency of electricity or light that goes across a network, a computer channel, or wireless. Control signals often traverse the same way as data in data communications, either as independent packets or embedded inside data packets.

Statement A: Whether data is read into or written out of CPU.

The 8085 Microprocessor provides RD and WR signals to initiate the read or write cycle. Because these Control Signals of 8085 are used both for reading/writing memory and for reading/writing an input device, it is necessary to generate separate read and write signals for memory and I/O devices.

Statement B: Whether the I/O device or memory is ready to transfer data.

Control signals are represented by thin lines. to transfer data from one register to another. Micro-operations are the elementary operations performed on Registers. Control signal indicates data the I/O device or memory is ready to transfer data. 

Hence the correct answer is A and B.

Additional InformationControl signal :

• Clocks and signals that establish communication channels and govern data flow are two forms of control signals.
• Control signal indicates data is read into or written out of CPU or the I/O device or memory is ready to transfer data. 
• When the device is ready for data transfer, the interface generates an interrupt request to the computer. 
• Control signals are transmitted between the two communicating units to indicate the time at which data is being transmitted. 
• The unit receiving the data item responds with another control signal to acknowledge receipt of the data. 

Concept:

The important assumption that is considered here is that all the three features are considered individually and not in effect of each other.

1. Data bus capability – If the bus size is increased, more words can be fetched and accommodated in a single CPU cycle. This ultimately affects the processing power of the system.
2. Addressing scheme – Optimising the addressing scheme can improve processing power hugely as some addressing schemes consume less processing time as compared to others. Similarly, poor choice of addressing scheme can affect the processing power.
3. Clock speed – As clock speed improves, the processing power goes up. Hence, both are inevitably linked.