 Hello, everyone, myself, Sanjay Udge, assistant professor, Department of Electronics Engineering, Valchan Institute of Technology, Solakpur. Today we are going to discuss Introduction to 8085 Microprocessor Part 1 Architecture. Learning outcome at the end of this session, students will be able to analyze architecture of 8085 microprocessor. Outline, introduction, 8085 microprocessor, 8085 architecture, question, answer, references. A microprocessor is a controlling unit of a microcomputer, fabricated on a small chip, capable of performing arithmetic logic unit, operations and communicating with the other devices connected to it. In this video, we will discuss the architecture of 8085 microprocessor. Basic microcomputer, the heart of this microcomputer is microprocessor that includes arithmetic logic unit, a register array and control unit. This microprocessor is connected to the input device as well as output device and the memory. So, this comprises a microcomputer. Microprocessor consists of an ALU that is arithmetic logic unit, a register array and control unit. ALU performs arithmetical and logical operations on the data received from the memory or an input device. A register array consists of registers identified by letters like B, C, D, E, HL and the accumulator. The control unit controls the flow of data and instructions within the computer. So, microprocessor consists of arithmetic logic unit, register array and control unit. For the temporary storage of the data, 8-bit registers are used named as B, C, D, E, H, L. The control unit performs all the necessary control actions required for the execution of the program. Microprocessor working, the microprocessor follows a sequence, fetch, decode and then execute initially. The instructions are stored in the memory in a sequential order. The microprocessor fetches those instructions from the memory, then decodes it and executes those instructions till stop instruction is reached. Later, it sends the result in binary to the output port. Between these processes, the register stores the temporary data and ALU performs the computing of functions. So, in summary, the working of the microprocessor consists of, before execution any single instruction, we have to fetch that instruction which is stored in the memory location. So, this has been carried out by the program counter. After fetching the instruction, the instruction is being stored in the instruction register. As the name suggests instruction register, it contains the instruction to be executed. After the instruction has been loaded into the instruction register, it has been decoded by instruction decoder. And then, control unit performs the necessary actions to activate the ALU to perform logical operations, to perform arithmetic operations. And meanwhile, the temporary data is stored in the register BCDHL and the accumulator. 8085 is pronounced as 8085 microprocessor. It is an 8-bit microprocessor designed by Intel in 1977 using NMOS technology. It has the following configuration, 8-bit data bus, 16-bit address bus which can address up to 64,000 bytes. A 16-bit program counter, 16-bit stack pointer, 6 8-bit registers arranged in pairs BCDHL. It requires plus 5V supply to operate at 3.2 MHz single phase clock. It is used in washing machine, microwave oven, mobile phone utases. The examples given over here, washing machine, microwave ovens. All these are programmable devices so that it requires the program to be stored. That is why we are using 8085 microprocessor to perform given operations. 8085 microprocessor functional unit. Accumulator, it is an 8-bit register used to perform arithmetic logic input output and load store operations. It is connected to internal data bus and ALU. ALU that is arithmetic logic unit. As the name suggests, it performs arithmetic and logical operations like addition, subtraction, ending, ordering, etc. on 8-bit data. General purpose registers. There are 6 general purpose registers in 8085 processor that is BCDHL. Each register can hold 8-bit data. These registers can work in pairs to hold 16-bit data and their pairing combination is like BCDHL. Program counter, it is a 16-bit register used to store the memory address location of the next instruction to be executed. Microprocessor increments the program counter whenever an instruction is being executed. So that the program counter points to the memory address of the next instruction that is going to be executed. So the program counter as discussed just now, it holds the memory address location of the next instruction to be fetched. Stack pointer, it is also a 16-bit register works like stack which is always incremented, decremented by 2 during push and pop operation. It is a part of the memory. Temporary register, it is 8-bit register which holds the temporary data of arithmetic and logic operations. Flag register, it is an 8-bit register having 5 single-bit flip-flops which holds either 0 or 1 depending upon the results stored in the accumulator. These are the set of 5 flip-flops. Each flip-flop is assigned for sine, then 0, auxiliary carry, parity and carry. Sine flip-flop is set when the result is positive. That means this flip-flop will have output equals to 1. If it is a negative, it will be reset to 0. If the result is 0, this flip-flop will be set. If it is non-zero, it will be logic 0. If auxiliary carry is generated in the operation, then this flip-flop is set. Otherwise, it is in the reset condition. For even parity result, this flip-flop is set. Otherwise, for odd parity, it will be store logic 0. And finally, if the carry is generated, this flip-flop will set to 1. Otherwise, it is reset to 0. Instruction resistor and decoder. It is an 8-bit resistor. When an instruction is fetched up, then it is been decoded. Timing and control unit. It provides timing and control signal to the microprocessor to perform operations, following other timing and control signals, which control external and internal circuits. Control signals, ready status signals, DMA signal, reset signal. Interrupt control. As the name suggests, it controls the interrupts during a process. When a microprocessor is executing a main program, and whenever an interrupt occurs, the microprocessor shifts the control from the main program to process the incoming request. After the request is completed, the control goes back to the main program. There are 5 interrupts, INTR, RSC 7.5, 6.5, 5.5 and trap. So, this is the block diagram of an architecture microprocessor 8085 microprocessor that includes ALU, then interrupt control, then 8-bit data bus, 16-bit address bus. In this, lower 8-bit address bus is used as a data bus, whereas higher-order 8-bits, that is AD-8 to AD-15, these are used only for the address bus. Here it has been shown as a program counter. This program counter holds the memory location of the next instruction to be fetched. Then, the instruction is being loaded into the instruction register, then it has been decoded, and after decoding the instruction, the control unit activates the signals that will control the overall operation like logical operations or arithmetic operations. These are the references. Thank you.