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Questions and Answers
Which operation is NOT performed by the Arithmetic and Logic Unit (ALU)?
Which operation is NOT performed by the Arithmetic and Logic Unit (ALU)?
What role does the Timing and Control Unit play in a microprocessor?
What role does the Timing and Control Unit play in a microprocessor?
Which register in the 8085 microprocessor holds the result of an ALU operation?
Which register in the 8085 microprocessor holds the result of an ALU operation?
What is the purpose of the register-pair formed by B and C in the 8085 microprocessor?
What is the purpose of the register-pair formed by B and C in the 8085 microprocessor?
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How many 8-bit general purpose registers does the Intel 8085 microprocessor contain?
How many 8-bit general purpose registers does the Intel 8085 microprocessor contain?
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Which of the following is the main function of registers in a microprocessor?
Which of the following is the main function of registers in a microprocessor?
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Which of the following registers is responsible for holding the address of the next instruction to be executed?
Which of the following registers is responsible for holding the address of the next instruction to be executed?
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What is the word length of the Intel 8085 microprocessor?
What is the word length of the Intel 8085 microprocessor?
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Which microprocessor was introduced in 1989?
Which microprocessor was introduced in 1989?
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In the 8085 microprocessor, what does the H-L register pair primarily act as?
In the 8085 microprocessor, what does the H-L register pair primarily act as?
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How many basic instructions does the Intel 8085 microprocessor have?
How many basic instructions does the Intel 8085 microprocessor have?
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Which microprocessor supports a clock frequency between 60-200 MHz?
Which microprocessor supports a clock frequency between 60-200 MHz?
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What is the pin count for the Intel 8085 microprocessor?
What is the pin count for the Intel 8085 microprocessor?
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Which evolution of microprocessor has a word length of 4-bit?
Which evolution of microprocessor has a word length of 4-bit?
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What is the typical clock cycle duration of the Intel 8085?
What is the typical clock cycle duration of the Intel 8085?
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What is the maximum memory addressing capacity of the Intel 8086?
What is the maximum memory addressing capacity of the Intel 8086?
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What happens to the carry flag in a subtraction operation when a borrow occurs?
What happens to the carry flag in a subtraction operation when a borrow occurs?
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Under what condition is the parity status flag set to 1?
Under what condition is the parity status flag set to 1?
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What does the auxiliary carry flag (AC) indicate?
What does the auxiliary carry flag (AC) indicate?
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When is the zero flag (Z) set to 1?
When is the zero flag (Z) set to 1?
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What does the sign flag (S) indicate about the result of an operation?
What does the sign flag (S) indicate about the result of an operation?
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What does the RESET IN function accomplish in a microprocessor?
What does the RESET IN function accomplish in a microprocessor?
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Which component is used to generate the clock for the microprocessor's operation?
Which component is used to generate the clock for the microprocessor's operation?
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What function does the ALE (address latch enable) signal perform in a machine cycle?
What function does the ALE (address latch enable) signal perform in a machine cycle?
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Which pins are used for the most significant bits (MSB) of memory address in Intel 8085?
Which pins are used for the most significant bits (MSB) of memory address in Intel 8085?
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What type of instruction is identified as having a word size of 1-byte?
What type of instruction is identified as having a word size of 1-byte?
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What is the role of the IO/M status signal in the Intel 8085 architecture?
What is the role of the IO/M status signal in the Intel 8085 architecture?
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What is indicated by the RESET OUT signal?
What is indicated by the RESET OUT signal?
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Which instruction is classified as a 2-byte instruction according to word size?
Which instruction is classified as a 2-byte instruction according to word size?
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In the context of instruction structure, what does the term 'opcode' refer to?
In the context of instruction structure, what does the term 'opcode' refer to?
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What does the SID input line signify in microprocessor operations?
What does the SID input line signify in microprocessor operations?
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What voltage does the Vcc supply provide to the microprocessor?
What voltage does the Vcc supply provide to the microprocessor?
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What operation is performed when $S_1 = 0$ and $S_0 = 0$?
What operation is performed when $S_1 = 0$ and $S_0 = 0$?
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What does the RD signal indicate when it goes low?
What does the RD signal indicate when it goes low?
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Which signal is used by a device to request access to the address and data buses?
Which signal is used by a device to request access to the address and data buses?
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What is indicated when the READY signal is sent to the microprocessor?
What is indicated when the READY signal is sent to the microprocessor?
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What does the HLDA signal indicate?
What does the HLDA signal indicate?
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Which of the following interrupts has the highest priority?
Which of the following interrupts has the highest priority?
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The INTRA signal is sent by the microprocessor when it receives which type of signal?
The INTRA signal is sent by the microprocessor when it receives which type of signal?
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What operation occurs when WR signal goes low?
What operation occurs when WR signal goes low?
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Which addressing mode allows the address of the operand to be specified by a register pair?
Which addressing mode allows the address of the operand to be specified by a register pair?
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Which instruction is an example of immediate addressing mode?
Which instruction is an example of immediate addressing mode?
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In register addressing mode, what is the primary characteristic of the operand?
In register addressing mode, what is the primary characteristic of the operand?
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What does the instruction 'STA 2400H' demonstrate?
What does the instruction 'STA 2400H' demonstrate?
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What is a defining feature of implicit addressing?
What is a defining feature of implicit addressing?
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In the instruction 'ADD B', what addressing mode is being used?
In the instruction 'ADD B', what addressing mode is being used?
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Which of the following instructions uses immediate addressing?
Which of the following instructions uses immediate addressing?
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What is the opcode representation for the instruction 'LDA 2500H'?
What is the opcode representation for the instruction 'LDA 2500H'?
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Study Notes
Introduction
- Microprocessor is a program-controlled semiconductor device, functioning as a computer's brain.
- It fetches, decodes, and executes instructions.
- It serves as the CPU in computers.
- An example of a microprocessor is the 8085.
- Intel created the 8085 in 1976.
Computer System Block Diagram
- A computer system comprises input devices, the CPU, memory, and output devices.
- Data flows from input devices to the CPU, then to memory, and finally to output devices.
- This diagram illustrates the fundamental structure of a computer system.
Types of Computers
- Computers are broadly categorized as analog and digital.
- Digital computers further classify into microcomputers, multiprocessor computers (or supercomputers).
- A microcomputer has one microprocessor.
- Examples include desktop, laptops, mobile phones, and notebooks.
Microcomputer
- A digital computer containing one microprocessor.
- Examples: Desktop, laptop, mobile phone, notebook.
- Microcomputers utilize a microprocessor as their central processing unit.
- They include components such as a keyboard, microprocessor (or CPU), memory, and a display unit.
Multiprocessor Computer
- A digital computer with more than one microprocessor.
- Examples: Desktop, laptops, mobile phones, notebooks.
Word Length of Microprocessor
- Word length is expressed in n-bits. Common values for n include 8, 16, 32, and 64.
- An 8-bit processor operates on 8-bit data at a time.
- Processing larger data (e.g., 16-bit) requires multiple operations by an 8-bit processor.
- Similarly, 16-bit and larger processors handle the data correspondingly.
- Larger word lengths enable faster and more complex operations.
Evolution of Microprocessor
- A table detailing different microprocessor models, their introduction years, word lengths, memory addressing capacity, pins, and clock frequencies is presented.
- Microprocessor models evolved from 4-bit to 64-bit types.
- Memory addressing capacity and clock frequencies increased over time.
Unit-I: Microprocessor 8085
- The Intel 8085 is an 8-bit NMOS microprocessor.
- It is a 40-pin IC (integrated circuit) housed on a single LSI chip..
- The 8085 operates using a +5 Vdc supply.
- Clock speed ranges from 3 MHz to 6 MHz.
- The clock cycle duration for the Intel 8085 AH-2 is 200 ns.
- The 8085 has 80 basic instructions and 246 opcodes.
- It functionally comprises an Arithmetic and Logic Unit (ALU), a Timing and Control Unit, and registers.
8085 Microprocessor Architecture
- A diagram illustrating the 8085 architecture is provided.
- Key components include the accumulator, temporary register, status flags, instruction register, arithmetic logic unit (ALU), timing and control unit, and other registers.
ALU (Arithmetic & Logic Unit)
- The ALU performs arithmetic and logical operations such as addition, subtraction, logical AND, logical OR, logical exclusive OR, complement, increment, decrement, shifts, rotations, and clear.
Timing and Control Unit
- The timing and control unit governs the entire operation of the microprocessor and connected peripherals.
- It controls the flow of data between the CPU and peripherals, including memory, and generates essential timing and control signals for instruction execution.
Registers
- Registers are temporary memory components of the microprocessor.
- Registers store data until transferred to memory or I/O (input/output) devices.
- Microprocessors with larger numbers of registers facilitate faster data transfer.
Specific 8085 Registers
- The 8085 microprocessor contains an 8-bit accumulator (register A), six 8-bit general-purpose registers (B, C, D, E, H, L), a 16-bit stack pointer, a 16-bit program counter, an instruction register, and a temporary register.
General-Purpose Registers
- The 8085 includes six 8-bit general-purpose registers (B, C, D, E, H, L).
- These registers can be paired (e.g., B-C, D-E, H-L) for 16-bit data storage or memory addressing.
Program Counter (PC)
- The 16-bit PC maintains the memory address of the next instruction to be executed.
Stack Pointer (SP)
- A 16-bit special register that controls stack addressing.
- It holds the address of the top element in the stack.
- The stack is a sequential memory for storing and retrieving data.
Instruction Register
- The instruction register holds the opcode of the current instruction being decoded and executed.
Temporary Register
- An 8-bit register associated with the ALU, used for storing data during arithmetic and logical operations.
Flags
- The Intel 8085 microprocessor includes five flip-flops used as status flags, reflecting ALU operation status.
- These flags include: Carry Flag (CS), Parity Flag (P), Auxiliary Carry Flag (AC), Zero Flag (Z), and Sign Flag (S).
8085 Pin Diagram
- Details of pins in the 8085 architecture are presented visually via a pin diagram.
- Pin descriptions detail functions like address bus (A8-A15), data bus (AD0-AD7), address enable (ALE), input/output (I/O) signal (IO/M), control signals (READY, HOLD), and interrupt lines.
Addressing Modes
- Different techniques to specify data for instructions are outlined.
- Modes include direct, register, register indirect, immediate, and implicit addressing.
Instruction Word Size, Addressing
- Instructions are classified as 1-byte, 2-byte, or 3-byte instructions based on their length.
- 1-byte instructions use immediate data, while 2-byte instructions involve addressing or data, and 3-byte instructions typically use larger data or addresses.
- Examples for each are provided.
Addressing Modes
- Instructions utilize specific addressing modes to specify data (e.g., direct, register, register indirect, immediate, implicit).
- Examples of various addressing modes are included.
Branch Group
- Unconditional and conditional branch instructions change the normal sequence of program execution.
- Instruction jump to a specified label/address.
Conditional Instructions
- Conditional jump instructions execute based on conditions (e.g., zero, carry, parity).
- Example instructions are outlined
Programming Example
- Assembly language code examples of data transfer, arithmetic operation, and other operations are presented
Subroutine Call and Return
-Instructions for subroutine calls (e.g., CALL addr) and subroutine returns (RET).
I/O & Machine Control Group
- Instructions for input and output operations (IN, OUT).
Miscellaneous Instructions
- Instructions like HLT (Halt).
Restart
- Restart instructions, enabling fast jumps to predetermined locations in the program.
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