8085 Assembly Language Programming
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Questions and Answers

Which register is primarily responsible for performing arithmetic and logical operations in the 8085 microprocessor?

  • Accumulator Register (correct)
  • Flag Register
  • Program Counter
  • Stack Pointer Register

    • What is the purpose of the Program Counter (PC) in the 8085 microprocessor?

  • To sequence the execution of program instructions (correct)
  • To count the number of cycles taken by an instruction
  • To point to the current instruction being executed
  • To store the result of arithmetic operations

    • Which flags are part of the Flag Register in the 8085 microprocessor?

  • Zero, Carry, Sign, Parity, and Auxiliary Carry flags (correct)
  • Sign and Negative flags
  • Zero and Overflow flags
  • Carry and Parity flags

    • How can the contents of a register be updated in the 8085 microprocessor when setting up a loop counter?

    <p>By using the INC and DEC instructions</p> Signup and view all the answers

    What does the Stack Pointer Register do in the 8085 microprocessor?

    <p>Points to the location in the stack memory</p> Signup and view all the answers

    Which operation is performed by the DCR instruction in the 8085 assembly language?

    <p>Decrement the contents of the register</p> Signup and view all the answers

    In the 8085 microprocessor's Flag Register, what does the Carry Flag indicate?

    <p>The result of an arithmetic operation required more bits than provided</p> Signup and view all the answers

    Which of the following best differentiates memory-mapped I/O from I/O-mapped I/O?

    <p>Only one allows the CPU to use addresses for both memory and I/O devices</p> Signup and view all the answers

    What is the maximum count a single register can achieve for loop operations?

    <p>255 times</p> Signup and view all the answers

    Which instruction is used to decrement a counter in a loop?

    <p>DCR</p> Signup and view all the answers

    In a loop using a register pair, how can one check if the count has reached zero?

    <p>By ORing the two registers and then checking the zero flag</p> Signup and view all the answers

    What is the primary function of the stack in the 8085 microprocessor?

    <p>To store temporary data during execution</p> Signup and view all the answers

    What does the POP instruction do in the context of the stack?

    <p>Increments the stack pointer and retrieves the item</p> Signup and view all the answers

    Which of the following correctly describes the operation of the MVI instruction?

    <p>It moves immediate data into a register</p> Signup and view all the answers

    How is the total delay calculated when accounting for both outside the loop and the loop itself?

    <p>T delay = TO + TL</p> Signup and view all the answers

    What happens to the stack pointer when data is pushed onto the stack?

    <p>It is decremented</p> Signup and view all the answers

    When using a delay loop with the instruction DCR C, how many T-States does it require per execution?

    <p>4 T-States</p> Signup and view all the answers

    What happens when the CALL instruction is executed in the 8085 microprocessor?

    <p>The current program counter is pushed onto the stack.</p> Signup and view all the answers

    What is one limitation of using a single register for looping?

    <p>Maximum count of 255 iterations</p> Signup and view all the answers

    What is the significance of the Last In First Out (LIFO) structure in the stack?

    <p>It means the last pushed item is the first to be retrieved</p> Signup and view all the answers

    What is the key function of the RET instruction in the 8085 microprocessor?

    <p>It restores the program counter from the stack.</p> Signup and view all the answers

    Which instruction is typically NOT associated with manipulating the stack?

    <p>ADD</p> Signup and view all the answers

    Which of the following best describes memory-mapped I/O in the context of the 8085 microprocessor?

    <p>I/O devices are treated as unique memory locations.</p> Signup and view all the answers

    What is a disadvantage of using memory-mapped I/O?

    <p>It limits the available memory addresses for other purposes.</p> Signup and view all the answers

    What does I/O-mapped I/O offer compared to memory-mapped I/O?

    <p>It provides a clearer separation between memory and I/O operations.</p> Signup and view all the answers

    Which instruction is used in memory-mapped I/O to read data from an input device?

    <p>IN</p> Signup and view all the answers

    In which scenario would using I/O-mapped I/O be preferred?

    <p>When memory addresses should be freed for data storage.</p> Signup and view all the answers

    Which of the following activities do both memory-mapped I/O and I/O-mapped I/O facilitate?

    <p>Interfacing the microprocessor with external devices.</p> Signup and view all the answers

    What is a potential drawback of I/O-mapped I/O?

    <p>It requires additional interpreting circuitry.</p> Signup and view all the answers

    What is a primary characteristic of memory-mapped I/O in relation to address availability?

    <p>Limits the available memory addresses for different functions</p> Signup and view all the answers

    Which type of I/O requires different commands for I/O operations?

    <p>I/O-Mapped I/O</p> Signup and view all the answers

    What aspect of I/O-Mapped I/O simplifies the hardware design?

    <p>Provides clearer separation between memory and I/O addresses</p> Signup and view all the answers

    How does address availability differ between memory-mapped I/O and I/O-mapped I/O?

    <p>I/O-mapped I/O has dedicated address space for I/O</p> Signup and view all the answers

    In the 8085 microprocessor, which interrupt is non-maskable and has the highest priority?

    <p>TRAP</p> Signup and view all the answers

    What is the effect of interrupts in the 8085 microprocessor?

    <p>They temporarily suspend normal program execution</p> Signup and view all the answers

    What is a limitation of memory-mapped I/O regarding port expandability?

    <p>Limited number of I/O ports available</p> Signup and view all the answers

    Which of the following interrupts is generated by an external device in the 8085 microprocessor?

    <p>TRAP</p> Signup and view all the answers

    How does memory-mapped I/O affect memory utilization?

    <p>It shares memory space with I/O devices</p> Signup and view all the answers

    What is one advantage of I/O-mapped I/O in terms of flexibility?

    <p>Greater flexibility in allocating memory for I/O devices</p> Signup and view all the answers

    In context of the 8085 microprocessor, what does INTR signify?

    <p>A maskable interrupt with lowest priority</p> Signup and view all the answers

    What is the function of the CALL signal when an interrupt is received in the 8085 microprocessor?

    <p>It directs control to the specific ISR</p> Signup and view all the answers

    Which address decoding technique ensures that each physical memory location is identified by a unique address?

    <p>Full address decoding</p> Signup and view all the answers

    How many interrupt signals are there in the 8085 microprocessor?

    <p>5</p> Signup and view all the answers

    What is an example of a non-maskable interrupt in the 8085 microprocessor?

    <p>TRAP</p> Signup and view all the answers

    What is the role of the SIM instruction in serial output data communication?

    <p>It outputs data through the SOD line.</p> Signup and view all the answers

    Which type of interrupt is characterized by a fixed vector address?

    <p>Vectored Interrupts</p> Signup and view all the answers

    Which instruction enables all interrupts in the 8085 microprocessor?

    <p>Enable Interrupt (EI)</p> Signup and view all the answers

    What is a potential disadvantage of using serial communication in the 8085 microprocessor?

    <p>Complex synchronization mechanisms are required.</p> Signup and view all the answers

    What is the main purpose of the interrupt service request (ISR)?

    <p>To handle the interrupt event</p> Signup and view all the answers

    How does the RIM instruction function with respect to serial input data?

    <p>It reads data from the SID line.</p> Signup and view all the answers

    Which of the following is a common application of serial I/O lines in the 8085 microprocessor?

    <p>Communication with external storage devices.</p> Signup and view all the answers

    Which of the following is a characteristic of maskable interrupts?

    <p>They can be ignored by the microprocessor</p> Signup and view all the answers

    What issue can arise from having multiple interrupts with different priorities?

    <p>Priority conflicts</p> Signup and view all the answers

    What issue may arise from using serial I/O lines due to the hardware limitations of the 8085 microprocessor?

    <p>Restricted number of connectable devices.</p> Signup and view all the answers

    What is a significant advantage of using the SID and SOD lines in a software-controlled I/O system?

    <p>They eliminate the need for input and output ports.</p> Signup and view all the answers

    Which instruction is used to read the status of hardware interrupts?

    <p>Read Interrupt Mask (RIM)</p> Signup and view all the answers

    Which statement correctly describes the relationship between SID and RIM instructions?

    <p>RIM manages data input through the SID line.</p> Signup and view all the answers

    What is a major benefit of using interrupts in a microprocessor?

    <p>Facilitating real-time processing</p> Signup and view all the answers

    What determines the vector address of hardware interrupts in the 8085 microprocessor?

    <p>It is calculated using the formula $8 * TYPE$</p> Signup and view all the answers

    Which of the following best characterizes the limitations of using serial communication in the 8085 microprocessor?

    <p>It is limited in data transfer rates.</p> Signup and view all the answers

    What is a common issue faced during asynchronous serial communication in the 8085 microprocessor?

    <p>Complex synchronization mechanisms.</p> Signup and view all the answers

    Which type of interrupt requires the interrupting device to provide the address of the sub-routine?

    <p>Non-Vectored Interrupts</p> Signup and view all the answers

    What is an example of a software interrupt in the 8085 microprocessor?

    <p>RST 2</p> Signup and view all the answers

    What role does the instruction 'Disable Interrupt (DI)' serve?

    <p>Resets the interrupt enable flip-flop</p> Signup and view all the answers

    Why is managing interrupt latency important in real-time systems?

    <p>It affects system responsiveness</p> Signup and view all the answers

    Which interrupts in the 8085 microprocessor can be masked or disabled?

    <p>Maskable Interrupts</p> Signup and view all the answers

    What is a consequence of interrupt nesting?

    <p>Complex interrupt handling and priority conflicts</p> Signup and view all the answers

    What is meant by interrupt overhead?

    <p>The time and resources needed to handle interrupts</p> Signup and view all the answers

    Which of the following is NOT a method of data transfer in the 8085 microprocessor?

    <p>Asynchronous data transfer scheme</p> Signup and view all the answers

    What does the Serial Data Input (SID) pin do in the 8085 microprocessor?

    <p>Inputs data serially into the microprocessor</p> Signup and view all the answers

    Why is interrupt-driven data transfer used?

    <p>It requires minimal timing knowledge of the device</p> Signup and view all the answers

    What protocol does the 8085 microprocessor use for serial communication?

    <p>Asynchronous serial communication protocol</p> Signup and view all the answers

    What defines the basic data transfer scheme?

    <p>It is beneficial when device timing characteristics are well known.</p> Signup and view all the answers

    Which of the following is a key advantage of using serial communication?

    <p>Less wiring required compared to parallel communication</p> Signup and view all the answers

    What role do the SIM and RIM instructions play in the 8085 microprocessor?

    <p>They control the transfer of serial data.</p> Signup and view all the answers

    What is a disadvantage of using an interrupt-driven data transfer method?

    <p>It can increase the number of interrupts generated.</p> Signup and view all the answers

    What does the SOD pin do in the 8085 microprocessor?

    <p>Outputs data serially from the microprocessor</p> Signup and view all the answers

    Which data transfer scheme checks the status of an input/output device before transferring data?

    <p>Status check data transfer</p> Signup and view all the answers

    How is serial communication affected by noise over long distances?

    <p>It experiences more signal degradation than parallel communication.</p> Signup and view all the answers

    What are the primary components used in serial data transfer in the 8085 microprocessor?

    <p>Two dedicated pins: SID and SOD</p> Signup and view all the answers

    Study Notes

    Assembly Language Programming of 8085

    • Assembly language is specific to a given processor, such as the 8085.
    • The 8085 has six general-purpose registers: B, C, D, E, H, and L.
    • Registers can be combined as register pairs (BC, DE, HL) for 16-bit operations.
    • The Accumulator (A) is a primary register used for arithmetic and logical operations within the Arithmetic Logic Unit (ALU).
    • The Flag Register is a part of the ALU, containing flags that reflect the status of recent operations.
      • Zero Flag (Z): Set if the result of the previous operation is zero.
      • Carry Flag (CY): Set if the previous operation resulted in a carry.
      • Sign Flag (S): Set if the previous result was a negative number.
      • Parity Flag (P): Set if the previous result had an even number of 1s.
      • Auxiliary Carry Flag (AC): Set if there was a carry from bit 3 to bit 4.
    • The Program Counter (PC) is a 16-bit register that stores the memory address of the next instruction to be fetched and executed.
    • The Stack Pointer Register (SP) is a 16-bit register that points to the top of the stack in memory.

    Counters and Time Delays

    • Counters are implemented using loops with increment (INR) or decrement (DCR) instructions.
    • Loop counters can use single registers or register pairs.
    • Time delays are calculated based on the number of T-states required by each instruction and the system clock frequency.
    • Delay loops create a specific delay using a loop structure with specific instructions.
    • The time delay of a loop is calculated by summing the individual delays within and outside the loop.

    Stack and Subroutine

    • The stack is a temporary storage area in memory used by the CPU for storing data like register values or information during program execution.
    • The stack is a Last In First Out (LIFO) data structure.
    • Stack instructions in 8085:
      • PUSH: This instruction pushes a register or memory location value onto the stack.
      • POP: This instruction removes the top item from the stack and copies it to the specified destination.
    • Subroutines are blocks of code that can be called and executed from different parts of the main program.
    • Subroutines can be used to reduce code redundancy and improve program organization.
    • Subroutine instructions in 8085:
      • CALL: This instruction jumps to a subroutine and saves the current program counter (PC) on the stack.
      • RET: This instruction returns from a subroutine by popping the saved program counter from the stack.

    Memory Mapped I/O and I/O Mapped I/O

    • Memory-mapped I/O directly uses memory addresses to communicate with peripheral devices.
    • The 8085 uses IN and OUT instructions to access I/O ports in memory.
    • I/O-mapped I/O uses separate address spaces for I/O operations and memory operations.
    • 8085 does not natively support I/O-mapped I/O, requiring additional circuitry for implementation.
    • Choosing between memory-mapped I/O and I/O-mapped I/O depends on the specific hardware and programming requirements.

    Address Decoding Techniques

    • Address decoding is the process of generating unique chip select (CS) signals for memory and peripheral devices based on the memory address.
    • Full address decoding uses all address lines to uniquely identify each memory location.
    • Partial address decoding uses a subset of address lines, allowing multiple addresses to point to the same location.
    • This technique is commonly used to save address space and simplify decoding logic.

    Interrupt System of 8085

    • Interrupts are signals that temporarily interrupt the normal program execution to handle external events or requests.

    • Five interrupt signals in the 8085:

      • TRAP: Non-maskable interrupt with the highest priority.
      • RST 7.5, RST 6.5, RST 5.5: Maskable interrupts generated by instructions.
      • INTR: Maskable interrupt generated by external devices.

    • Interrupt types can be categorized into:

      • Hardware/Software: Based on whether the interrupt is generated by hardware or software.
      • Vectored/Non-vectored: Based on whether the interrupt handler address is fixed or specified by the interrupting device.
      • Maskable/Non-maskable: Based on whether the interrupt can be ignored or disabled.### Interrupts in 8085 Microprocessor

    • TRAP is a non-maskable interrupt triggered by both level and edge changes.

    • It is used in critical power failure conditions.

    • The 8085 prioritizes interrupts for simultaneous requests.

    • Interrupt Instructions:

      • EI (Enable Interrupt): Enables all interrupts, except TRAP, after the execution of the next instruction.
      • DI (Disable Interrupt): Disables all interrupts.
      • SIM (Set Interrupt Mask): Used to configure hardware interrupts (RST 7.5, RST 6.5, RST 5.5) and manage the Serial Output Data (SOD) line.
      • RIM (Read Interrupt Mask): Reads the status of hardware interrupts and the Serial Input Data (SID) line into the accumulator.

    Uses of Interrupts

    • Real-time processing: Responds quickly to external events like user input and hardware signals.
    • Multi-tasking: Allows the microprocessor to handle multiple tasks by temporarily suspending the current task and executing the interrupting event's ISR.
    • Input/Output operations: Manages data transfer between the microprocessor and external devices.
    • Error handling: Detects and recovers from hardware or software errors.
    • Power management: Puts the microprocessor into low-power mode when not needed and wakes it up with interrupts.

    Issues with Interrupts

    • Priority conflicts: Can occur when multiple interrupts happen simultaneously with different priority levels.
    • Race conditions: Occur when multiple processes attempt to access the same resources concurrently.
    • Interrupt latency: The delay between an interrupt and the start of its ISR execution. Can affect responsiveness and real-time performance.
    • Interrupt nesting: When an interrupt happens while another interrupt's ISR is being executed. Can lead to complex handling and conflicts.
    • Interrupt overhead: The additional processing time and resources required to handle interrupts.

    Data Transfer Schemes

    • Data transfer schemes facilitate communication between the 8085 and external devices. They use Input/Output ports to systematically transfer data.
    • Data Transfer Types:
      • Parallel: Data transferred simultaneously through multiple lines.
        • Programmed Input/Output: Uses instructions to transfer data directly.
        • Direct Memory Access (DMA): Allows the external device to access memory directly.
      • Serial: Data transferred bit-by-bit over a single line.
    • Types of Data Transfer Methods:
      • Basic or Simple: Used when accurate knowledge of timing characteristics is available.
      • Status Check: Used when timing characteristics are unknown, requiring a status check before transferring.
      • Interrupt Driven: Used when timing characteristics are variable and the processor waits for the device to be ready.

    Serial Data Transfer Through SOD and SID Lines

    • The 8085 uses the Serial Output Data (SOD) and Serial Input Data (SID) lines for serial communication.
    • SOD: Outputs serial data controlled through the SIM instruction.
    • SID: Inputs serial data controlled through the RIM instruction.
    • Advantages: Eliminates the need for separate input and output ports.

    Issues with Serial I/O Lines

    • Limited data transfer rates: Serial communication is slower than parallel communication.
    • Data transmission errors: More susceptible to errors due to noise or interference.
    • Complex synchronization: Requires complex synchronization mechanisms for accurate asynchronous serial communication.
    • Interrupt handling: Requires careful interrupt handling to prevent data loss or corruption.
    • Hardware limitations: The 8085 has a limited number of pins for serial communication.

    Uses of Serial I/O Lines

    • Interfacing with sensors and actuators: Commonly used for data transfer with these devices.
    • Data logging and storage: Transfers data to and from memory chips.
    • Industrial automation: Facilitates communication between components in industrial automation systems.
    • Communication with peripherals: Used to interact with devices such as printers, displays, and modems.
    • Networking: Establishes network connections between devices.

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    Description

    Test your knowledge on 8085 Assembly Language programming, focusing on its registers, accumulator, flag register, and program counter. This quiz will help you understand the fundamental concepts and operations used within the 8085 microprocessor architecture.

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