Assembly Language Programming of 8085
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Questions and Answers

Which register is responsible for storing the results of arithmetic and logical operations in the 8085 microprocessor?

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

    • What is the role of the Flag Register in the 8085 microprocessor?

  • Contains the stack memory address
  • Stores the next instruction address
  • Indicates the status of operations and assists in decision-making (correct)
  • Holds the result of the last operation

    • How does the Program Counter (PC) operate during instruction fetching?

  • It is decremented after fetching an instruction.
  • It is incremented to point to the next instruction after fetching. (correct)
  • It points to the current instruction byte only.
  • It stores values of the registers being operated on.

    • When loading a loop counter in the 8085, which instructions are typically used to modify the contents?

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

    Which of the following is NOT one of the five flags found in the Flag Register of the 8085 microprocessor?

    <p>Negative Flag (N)</p> Signup and view all the answers

    What are the general-purpose registers used in the 8085 microprocessor?

    <p>B, C, D, E, H, L</p> Signup and view all the answers

    What is the primary function of the Stack Pointer Register in the 8085 architecture?

    <p>To define the beginning of the stack in memory</p> Signup and view all the answers

    Which transition happens to the Program Counter when the 8085 microprocessor fetches the current instruction?

    <p>It is incremented to point to the next instruction.</p> Signup and view all the answers

    Which instruction is used to enable interrupts in the 8085 microprocessor?

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

    What is a primary characteristic of non-vectored interrupts?

    <p>They are defined by the interrupting device.</p> Signup and view all the answers

    Which of the following interrupts in the 8085 microprocessor is classified as non-maskable?

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

    How is the vector address for vectored interrupts calculated in the 8085 microprocessor?

    <p>8 * TYPE INTERRUPT</p> Signup and view all the answers

    What are maskable interrupts capable of in the 8085 microprocessor?

    <p>Being ignored by the processor when disabled</p> Signup and view all the answers

    What is a key concern related to using interrupts in the 8085 microprocessor that affects system performance?

    <p>Interrupt latency</p> Signup and view all the answers

    Which statement about the instruction Read Interrupt Mask (RIM) is true?

    <p>It reads the status of the hardware interrupts.</p> Signup and view all the answers

    Which of the following is NOT a function of interrupts in the 8085 microprocessor?

    <p>Compiling programs</p> Signup and view all the answers

    Which of the following hardware interrupts is NOT part of the 8085 microprocessor?

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

    What allows the microprocessor to maintain orderly execution of ISRs when multiple interrupts are detected?

    <p>Priority of Interrupts</p> Signup and view all the answers

    What aspect of interrupts could lead to race conditions in an 8085 microprocessor system?

    <p>Simultaneous access to resources</p> Signup and view all the answers

    What needs to be considered to avoid issues with priority conflicts among interrupts?

    <p>Carefully designing and testing interrupt priorities</p> Signup and view all the answers

    What is one major advantage of I/O-Mapped I/O over Memory-Mapped I/O in the 8085 microprocessor?

    <p>It uses dedicated addresses for I/O operations.</p> Signup and view all the answers

    How many hardware interrupts are there in the 8085 microprocessor?

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

    Which aspect limits the available memory addresses for different functions in Memory-Mapped I/O?

    <p>Shared memory addresses</p> Signup and view all the answers

    Which interrupt in the 8085 microprocessor has the highest priority?

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

    Which bit pattern is most likely to be involved in the Set Interrupt Mask (SIM) process?

    <p>Various bits to form masks</p> Signup and view all the answers

    Which characteristic of I/O-Mapped I/O contributes to a clearer separation of memory and I/O addresses?

    <p>Separate address areas</p> Signup and view all the answers

    What is a disadvantage of Memory-Mapped I/O regarding address availability?

    <p>It reduces the total available memory space.</p> Signup and view all the answers

    In what way does I/O-Mapped I/O improve flexibility in memory allocation?

    <p>By utilizing dedicated address spaces.</p> Signup and view all the answers

    How does the instruction set differ between Memory-Mapped I/O and I/O-Mapped I/O?

    <p>Both use the same set of commands.</p> Signup and view all the answers

    What interrupt signal can be generated by a hardware malfunction in the 8085 microprocessor?

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

    Which addressing technique uses all the address lines to specify a unique memory location?

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

    What is the main drawback of using I/O ports in Memory-Mapped I/O?

    <p>Limited address flexibility.</p> Signup and view all the answers

    Which feature allows I/O-Mapped I/O to accommodate a larger number of I/O ports?

    <p>Separate memory addresses</p> Signup and view all the answers

    What complicates the hardware of I/O-Mapped I/O systems?

    <p>The need for additional interpreting circuitry.</p> Signup and view all the answers

    In the 8085 microprocessor, what action occurs when an interrupt signal is received?

    <p>Current execution is suspended, and control goes to an ISR.</p> Signup and view all the answers

    What is the primary purpose of the CALL instruction in the 8085 microprocessor?

    <p>To call a subroutine</p> Signup and view all the answers

    What is one of the primary challenges associated with interrupt nesting?

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

    How does the RET instruction function in the context of subroutines?

    <p>It pops the top item from the stack into the program counter</p> Signup and view all the answers

    Which of the following accurately defines memory-mapped I/O in the 8085 microprocessor?

    <p>I/O ports use unique memory addresses for access</p> Signup and view all the answers

    What kind of data transfer scheme is characterized by the processor checking device readiness?

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

    What is a disadvantage of memory-mapped I/O as compared to I/O-mapped I/O?

    <p>It limits the number of memory addresses available for general use</p> Signup and view all the answers

    Which pin on the 8085 microprocessor is used for serial data input?

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

    What is a notable disadvantage of high interrupt overhead in a system?

    <p>Decreased system performance</p> Signup and view all the answers

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

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

    What challenge arises from the use of I/O-mapped I/O in the 8085 microprocessor?

    <p>It necessitates extra decoding circuitry</p> Signup and view all the answers

    Which data transfer method is most suitable when the timing characteristics of the Input Output device are known?

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

    Why might a programmer prefer to use memory-mapped I/O over I/O-mapped I/O?

    <p>It simplifies programming by treating I/O devices as memory locations</p> Signup and view all the answers

    What feature distinguishes serial communication in the 8085 microprocessor?

    <p>Uses SID and SOD pins for communication</p> Signup and view all the answers

    What is a significant advantage of using I/O-mapped I/O?

    <p>It allows larger address spaces for both memory and I/O</p> Signup and view all the answers

    Which of these is NOT a reason for using serial I/O over parallel communication?

    <p>Complex hardware requirements</p> Signup and view all the answers

    When using interrupt driven data transfer, what problem occurs due to unknown timing characteristics?

    <p>Processor idling while waiting</p> Signup and view all the answers

    In the context of the 8085 microprocessor, which of the following statements is true regarding the stack?

    <p>The stack allows for returning from subroutines</p> Signup and view all the answers

    What does the Serial Control (SOD) pin indicate during serial communications?

    <p>The beginning of a data transfer operation</p> Signup and view all the answers

    What does the IN instruction accomplish in the 8085 microprocessor when used with memory-mapped I/O?

    <p>It transfers data from an I/O port to the accumulator</p> Signup and view all the answers

    Why are lower-priority interrupts typically disabled during critical operations?

    <p>To avoid priority conflicts</p> Signup and view all the answers

    What can significantly impact system performance when there are frequent interrupts?

    <p>Introduction of interrupt overhead</p> Signup and view all the answers

    What is one of the major advantages of using Serial I/O lines in microprocessor communication?

    <p>Fewer wires required for communication</p> Signup and view all the answers

    Which statement about data transfer schemes in the 8085 microprocessor is true?

    <p>Different schemes are optimized for varying timing knowledge.</p> Signup and view all the answers

    What is the primary purpose of the SIM instruction in the context of Serial Output Data (SOD)?

    <p>To output the carry bit through the SOD line.</p> Signup and view all the answers

    Which limitation is commonly associated with serial I/O lines in the 8085 microprocessor?

    <p>Limited data transfer rates compared to parallel communication.</p> Signup and view all the answers

    What role does the RIM instruction play in serial input data processing?

    <p>It enables input of data through the SID line.</p> Signup and view all the answers

    Why might data transmission errors occur more frequently in serial communication?

    <p>Because of its susceptibility to noise and interference.</p> Signup and view all the answers

    In what scenario might the limited number of pins on the 8085 microprocessor pose a challenge?

    <p>When attempting to connect multiple devices using serial communication.</p> Signup and view all the answers

    How does asynchronous serial communication complicate the design of the 8085 microprocessor systems?

    <p>By necessitating complex synchronization mechanisms.</p> Signup and view all the answers

    Which of the following is NOT a common use for serial I/O lines in the 8085 microprocessor?

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

    What advantage does the SID and SOD lines provide 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 aspect of serial I/O lines is particularly beneficial in industrial automation?

    <p>They provide a reliable method for data transfer between components.</p> Signup and view all the answers

    What is the maximum count a loop can repeat using a single register in the 8085 microprocessor?

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

    How does the 8085 microprocessor determine when to exit a loop using a register pair?

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

    What is the delay calculation formula used to determine the time in a delay loop?

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

    In the provided example of a delay loop, how many T-States does the JNZ instruction take in its final iteration?

    <p>7 T-States</p> Signup and view all the answers

    Which of the following operations can the stack in the 8085 microprocessor perform?

    <p>Push and pull</p> Signup and view all the answers

    What is the role of the Stack Pointer (SP) in the 8085 microprocessor?

    <p>It points to the next item to push onto the stack</p> Signup and view all the answers

    What is the primary benefit of using subroutines in programming?

    <p>To reuse code efficiently and simplify complex problems</p> Signup and view all the answers

    In the 8085 microprocessor, what happens to the Stack Pointer during the PUSH operation?

    <p>It decrements by one</p> Signup and view all the answers

    Why might data recovery from the stack in a subroutine need to be done in reverse order?

    <p>To sustain the Last In First Out (LIFO) structure</p> Signup and view all the answers

    When using a loop constructed with a conditional jump, what determines whether the jump occurs?

    <p>The termination count of the loop counter</p> Signup and view all the answers

    How many T-States does an MVI instruction require in the 8085 microprocessor example?

    <p>7 T-States</p> Signup and view all the answers

    What is necessary to adjust if you want to achieve an accurate delay calculation in a loop?

    <p>You need to subtract delay caused by the final instruction</p> Signup and view all the answers

    Which instruction is used to pop data from the stack in the 8085 microprocessor?

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

    Study Notes

    Assembly Language Programming of 8085

    • Assembly language is specific to a given processor.
    • 8085 assembly language is different from Motorola 6800 microprocessors.
    • Microprocessors cannot understand assembly language.
    • An assembler converts an assembly language program to machine language.

    8085 Architecture

    • Contains six general-purpose registers: B, C, D, E, H, L
    • Register pairs can perform 16-bit operations (BC, DE, HL).
    • Accumulator register (A) is part of the ALU, used for 8-bit data storage, arithmetic, and logic operations.
    • Flag register is also part of the ALU.
    • 8085 has five flags: Zero (Z), Carry (CY), Sign (S), Parity (P), and Auxiliary Carry (AC).
    • Flags are set or reset during arithmetic or logic operations and can be tested by software instructions.
    • Program counter (PC) is a 16-bit register that sequences program instruction execution, storing the address of the next instruction to be fetched.
    • Stack pointer (SP) is a 16-bit register that points to a location in stack memory.

    Counters and Time Delays

    • Counters are implemented using registers with a specific value.
    • DCR (decrement) and INR (increment) instructions update register contents.
    • Conditional jump instructions create loops that iterate based on a counter value.
    • Using DCR instruction for a loop counter:
      • MVI C, 15H
      • LOOP DCR C
      • JNZ LOOP
    • Using a register pair for a loop counter increases the maximum count to 65,535.
    • Example loop with a register pair:
      • LXI B, 1000H
      • LOOP DCX B
      • MOV A, C
      • ORA B
      • JNZ LOOP
    • Each instruction uses a specific number of T-states (clock cycles) to execute.
    • Delay = No. of T-States / Frequency
    • Delay loops are used to introduce time delays within a program.

    Stack and Subroutines

    • Stack:
      • Special area of memory used by the CPU to temporarily store register information and general data during execution.
      • LIFO (Last-In, First-Out) structure managed using push and pop operations.
      • Stack Pointer (SP) register contains the 16-bit offset for the top of the stack.
    • Subroutines:
      • Reusable blocks of code that can be called multiple times from different parts of a program.
      • Improve code organization and reduce redundancy.
      • CALL instruction: Jumps to the subroutine and saves the current program counter on the stack.
      • RET instruction: Returns from the subroutine by popping the saved program counter.

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

    • I/O addressing techniques determine how a microprocessor interacts with external peripherals.
    • Memory-mapped I/O:
      • Peripherals are accessed using the same memory addresses as RAM.
      • IN and OUT instructions transfer data between the accumulator and specific I/O addresses.
      • Simpler programming, but limits memory address space for general use.
    • I/O-mapped I/O:
      • Peripherals have dedicated address spaces separate from memory addresses.
      • Use specific instructions for I/O access.
      • Offers clearer separation, larger address space, and improved control.

    Address Decoding Techniques

    • Address decoding ensures that only one memory-mapped component receives the information for a given address.
    • Address bus lines are divided into two sections:
      • Most significant bits generate chip select (CS*) signals.
      • Least significant bits are used as device addresses.
    • Full address decoding:
      • Every unique memory location is identified by a specific address.
    • Partial address decoding:
      • Multiple addresses can correspond to the same physical memory location.
      • Used to minimize memory chip usage when the entire address range is not required.

    Interrupt System of 8085

    • Interrupts:

      • Signals that temporarily halt normal program execution and transfer control to a dedicated ISR (Interrupt Service Routine).

    • Interrupt Types:

      • TRAP: Non-maskable, highest priority, triggered by events like power failures.
      • RST 7.5, RST 6.5, RST 5.5: Maskable, triggered by software instructions.
      • INTR: Maskable, lowest priority, triggered by external devices like peripherals.

    • When an interrupt occurs:

      • Microprocessor acknowledges the interrupt.
      • Control transfers to the specified ISR.
      • RET instruction returns control back to the interrupted program.### TRAP Interrupt

    • TRAP interrupt is non-maskable, used in critical power failure conditions.

    • Supported by both level and edge triggering.

    Interrupt Priority

    • When multiple interrupts occur, the microprocessor executes the interrupt service request (ISR) based on interrupt priority levels.

    Interrupt Instructions

    • Enable Interrupt (EI): Enables interrupts, except for the TRAP interrupt.
    • Disable Interrupt (DI): Disables all interrupts.
    • Set Interrupt Mask (SIM): Used to set interrupt masks for hardware interrupts (RST 7.5, RST 6.5, RST 5.5) and generate output data through the Serial Output Data (SOD) line.
    • Read Interrupt Mask (RIM): Reads the status of hardware interrupts and the SID line.

    Uses of Interrupts in the 8085 Microprocessor

    • Real-time processing: Responds quickly to external events.
    • Multi-tasking: Enables simultaneous execution of multiple tasks via interrupts.
    • Input/output operations: Handles data transfer between the microprocessor and external devices.
    • Error handling: Detects and recovers from hardware or software errors.
    • Power management: Controls power states of the microprocessor, putting it in low-power mode when idle.

    Issues with Interrupts

    • Priority conflicts: Multiple interrupts with different priorities occurring simultaneously could lead to system failure.
    • Race conditions: Multiple processes competing for resources can lead to incorrect results.
    • Interrupt latency: The time delay between interrupt occurrence and ISR execution can impact system responsiveness.
    • Interrupt nesting: An interrupt occurring while another ISR is running can cause complex handling and priority issues.
    • Interrupt overhead: Processing time and resources used to handle interrupts can affect system efficiency.

    Data Transfer Schemes

    • Programmed Input/Output: Data transfer using programmed instructions.
    • Direct Memory Access (DMA): Transfers data directly between memory and external devices.
    • Parallel Data Transfer: Transfers data using multiple wires simultaneously.
      • Basic/Simple: Direct transfer, requires knowledge of timing characteristics.
      • Status Check: More complex, used when timing information is not available.
      • Interrupt-driven: Used when timing characteristics are unknown and the device takes time to become ready.

    Serial Data Transfer (SOD and SID Lines)

    • The 8085 has two dedicated pins for serial communication: Serial Output Data (SOD) and Serial Input Data (SID).
    • They use the asynchronous start-stop communication protocol where data is transmitted as bits with start and stop bits.
    • SIM instruction: Enables serial output using the SOD line.
    • RIM instruction: Enables serial input using the SID line.

    Advantages of Serial Communication

    • Cost-effective: Requires fewer wires compared to parallel communication.
    • Compatibility: Works with various devices using serial communication protocols.
    • Long distances: More reliable for data transmission over long distances.
    • Simplified: Simplifies data transfer and reduces hardware complexity.
    • Flexibility: Allows flexibility with baud rate, data format, and communication parameters.

    Issues with Serial I/O

    • Limited data transfer rates: Slower than parallel communication.
    • Transmission errors: More prone to errors in noisy environments.
    • Synchronization complexity: Asynchronous communication requires complex synchronization mechanisms.
    • Interrupt handling: Requires careful interrupt handling to avoid data loss.
    • Hardware limitations: The 8085 has a limited number of pins, restricting the number of devices connected through serial communication.

    Uses of Serial I/O Lines

    • Sensors and actuators: Commonly used for communication with these devices.
    • Data logging: Transfer data to and from memory devices.
    • Industrial automation: Used for data transfer in industrial automation systems.
    • Peripherals communication: Allows communication with printers, displays, and modems.
    • Networking: Establishes network connections between devices.

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    Description

    Explore the fundamentals of assembly language specific to the 8085 microprocessor. Understand the architecture, including key registers such as the accumulator and the function of the program counter. This quiz will help you assess your knowledge of microprocessor programming and its components.

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