Microprocessor Fundamentals (DERS 2223)

Random Access Memory (RAM) is the main memory used by the computer to store data and programs that are currently in use. It allows for quick access to any location in memory.

Read Only Memory (ROM) is a special type of memory that holds permanent data, like the BIOS, which is needed to start the computer. This data cannot be altered by the user.

RAM is volatile, meaning data is erased when the computer is turned off, whereas ROM is non-volatile and retains its information even when the power is off.

A system's way of connecting with the outside world. They transfer data between the computer and external devices.

Input devices are tools that allow us to send information to the computer, like a keyboard or a mouse.

Output devices display or present information from the computer to the user, like a monitor or printer.

The Intel 8085 is an 8-bit microprocessor released in 1976. It can access up to 64 kilobytes of memory.

The 8085 is chosen for teaching because it's widely used, easy to understand, and has a simple architecture, making it ideal for learning basic programming concepts.

The 8085 microprocessor has 40 pins, which are used for various functions to interact with external devices and the system.

Pins of the 8085 microprocessor are divided into 6 categories: Address bus, data bus, control and status bus, power supply, externally initiated and acknowledgment signals, and serial I/O ports.

The address bus in the 8085 microprocessor consists of 16 signal lines which are used to identify the specific memory location or I/O device where data is to be transferred.

The 8085 microprocessor has a 16-bit address bus, which allows it to access 2^16 (65,536) memory locations or I/O devices. It uses this to uniquely address each location in the system's memory.

The data bus in the 8085 microprocessor allows the transfer of information (data) between the microprocessor and other components like memory or I/O devices.

The control and status bus lines in the 8085 are responsible for controlling the operations of the microprocessor and providing status information about ongoing operations. Signals like 'Read' and 'Write' are part of this bus.

The 8085 microprocessor requires power supply voltage to function. The VCC pin provides the positive voltage supply, while the GND pin serves as the ground reference point.

External signals, such as interrupts, allow other devices to communicate with the 8085 to temporarily pause the current operation and handle an urgent request.

The data bus is a group of 8 lines used to transmit data between the microprocessor and other components. It allows the 8085 to move data one byte (8 bits) at a time.

The control bus handles commands and status information between the microprocessor and other components. It ensures smooth coordination of operations.

WR* (Write) is a control signal that tells the selected memory or I/O device to receive data from the microprocessor. It's also an active low signal.

IO/M* (Input/Output or Memory) is a status signal that distinguishes between I/O (input/output) and memory operations. It's high for I/O operations and low for memory operations.

ALE (Address Latch Enable) is a positive-going pulse that signals the start of an operation and indicates that the address bits are available on the address bus.

Vcc (Voltage, Common Collector) is the positive power supply for the microprocessor, typically 5 volts.

X1 and X2 are pins where a crystal oscillator is connected to provide a stable clock signal for the microprocessor. The frequency of the crystal is usually twice the desired operating frequency.

The 8085 microprocessor uses a 16-bit address bus to access memory locations and peripherals. It consists of 16 address lines, including 8 high-order address lines (A15-A8) and 8 low-order address lines (AD7-AD0) that are multiplexed with the data bus.

The high-order address lines (A15-A8) on the 8085 address bus are unidirectional and used to determine the most significant bits of a 16-bit address. This helps select the correct memory bank or I/O device.

The low-order address lines (AD7-AD0) on the 8085 address bus are bidirectional, meaning they can be used for both address and data transfer. During the first clock cycle they are address lines, and during the second and third clock cycles they function as data lines.

The Address Latch Enable (ALE) signal is a control signal that determines whether the AD7-AD0 lines are used for addressing or data transfer. When ALE is high, they function as address lines, and when ALE is low, they function as data lines.

The 8085 microprocessor has an 8-bit data bus, which means it can transfer 8 bits of data at a time. The AD7-AD0 lines serve as the data bus after the initial address cycle, carrying the binary information.

The 8085 microprocessor uses multiplexing to share the AD7-AD0 lines for both address and data transfer. This saves pins and allows the microprocessor to be smaller and more efficient.

The 8085 memory space is addressed using 16 bits, giving a range from 0000 to FFFF, which is equivalent to 64 kilobytes (kB).

To calculate the number of address lines required for a given memory capacity, you use the formula: x = log(memory capacity)/log(2). For example, an 8 kB memory chip requires 13 address lines.

The ALU (Arithmetic Logic Unit) is the brain of the 8085 microprocessor. It performs all the arithmetic and logic operations like addition, subtraction, AND, OR, XOR, and incrementing numbers. It's like the math whiz of the computer!

The Accumulator is a special 8-bit register within the ALU. It's used to store the results of arithmetic and logic operations. Imagine it as a temporary storage space for the ALU's calculations.

The temporary register acts like a scratchpad for the ALU. It holds data during calculations, allowing the ALU to process and manipulate information efficiently. Think of it as a temporary work space for the ALU.

The status register is like a status board for the ALU. It stores information about the results of operations, including carry, parity, auxiliary carry, sign, and zero flags. These flags help determine the outcome of operations and guide further processing.

The 8085 microprocessor has a special memory area called the stack. It's a temporary storage space used to store data during program execution, particularly when function calls or subroutine calls are made. Imagine it as a temporary storage box for data during program execution.

The Timing and Control Unit is responsible for coordinating and controlling all the activities within the 8085 microprocessor. It generates the timing signals needed for proper operation, manages the execution of instructions, and oversees all the internal activities. It's like the conductor of the microprocessor's orchestra.

The Instruction Register and Decoder are responsible for understanding the instructions given to the 8085 microprocessor. They receive the instructions, decode them, and then translate them into actions that the microprocessor can understand. It's like the interpreter of the microprocessor.

The Register Array contains a collection of general-purpose registers used by the 8085 microprocessor to store data temporarily during program execution. These registers are like small, efficient storage spaces for the microprocessor. It's like the collection of drawers in the microprocessor.

An 8-bit register that acts as the primary data storage and processing unit within the 8085 microprocessor. It's involved in arithmetic and logical operations.

A set of six 8-bit registers (B, C, D, E, H, L) used for storing various binary values. They can also be paired for 16-bit operations.

A 16-bit register that serves as a memory pointer for a special data structure called the "stack." It manages the stack's address during function calls and data storage.

A 16-bit register responsible for keeping track of the memory address of the next instruction to be executed. It essentially controls the flow of program execution.

A 16-bit register that temporarily holds the address of a memory location being accessed during data transfers.

A register that contains information about the status of the microprocessor, such as whether an operation resulted in a carry or a zero flag. These flags are used in conditional branching and decision-making during program execution.

A temporary register that is used for holding data during intermediate stages of processing. It is not generally accessible by programming instructions.

The registers in the 8085 are implemented using flip-flops, which are a type of electronic circuit designed to store a single bit of information. Each flip-flop acts as a basic memory element, allowing the registers to hold data.