 Hello everyone, this is Vishwanath Chauhan from Computer Science and Engineering department waltz in the Institute of Technology, SolarPool. Now I am here to explain the architecture of microprocessor 8085. At the end of this session, the students will be able to understand how microprocessor 8085 works and they will explain the working of 85 architecture. Let us have a glance on architecture. So there is a accumulator register which is 8 bit in width. There is another temperature register which is also 8 bit in width. So operands are coming from these two registers from accumulator and temperature register. And these input data are forwarded to arithmetic and logic unit of microprocessor 8085. So this unit performs the arithmetic or logical operations on these data. With respect to this, it will generate the subsequent result and result will be forwarded through 8 bit internal data bus towards accumulator or it may be stored in memory. So it depends on instruction. So after performing arithmetic or logical operation, the subsequent flags are going to set or reset. So 8085 has five flags. So depends on operation, the respective flags are going to set or reset. So the instructions are stored in memory and those instructions are fetched and it will be stored in IR which is instruction register. So fetched instructions are stored in instruction register. So that it is going to forward towards instruction decoder and machine cycle encoding where decoding of instruction takes place. There is a timing and control unit which is going to generate the appropriate signal so that all other units performs their task. Then it generates the signals like read, write, io slash mbar, status signals as 0, s1, etc. There is a register array. So those registers are bc, d, e, h, l, sp, pc. So these are bc, b8bit, c8bit, d, e, h, l, these are 8-bit registers. Depends on requirement, these 8-bit registers are paired like bc, d, e and hl so that it acts as a 16-bit register pair. So sp is a 16-bit register, pc is a 16-bit register. And there is an increment or decrement address slash circuit. So there is address buffer or address or data buffer in which the address and data are stored subsequently it is forwarded further. There is an interrupt controller circuit. So this is going to control the five main hardware interrupts such as RS3 7.5, RS3 6.5, RS3 5.5, INTR, TRAP. For INTR it gives the acknowledgement as INTA bar. There is one more control circuit which is serial Ivo. So it is having two pins serial IN and serial OUT data. So this is mainly designed to have a communication between microprocessor and external device. The communication takes place in serial way that is at a particular time single bit is transferred. So we will see further regarding 8085. 8085 is called as 8085 microprocessor. It is an 8-bit microprocessor designed by Intel in 1977 by using NMOS technology. It is having following features. It has 8-bit data bus which carries 8-bit data. It has 16-bit address bus which can address up to 2 raised to 16 that is 64 kb. It is having 16-bit program counter PC register. It has 16-bit tag pointer called SP. It has general purpose registers, BCDHL. It requires plus 5 volt power supply, top right side 3 mhz clock frequency. It is used in washing machines, microwaves, mobile phones, etc. So let us have a glance on functional unit of microprocessor 8085. It has accumulator, arithmetic and logic unit, general purpose register, program counter, stack pointer, temp register, flag register, instruction register and decoder, timing and control unit, interrupt control, serial input output control, address buffer and address data buffer, address bus and data bus. So let us have this functional unit one by one, accumulator. It is an 8-bit register used to hold 8-bit of data, arithmetic and logic unit. It performs arithmetic and logical operations like addition, subtraction and or etc. on 8-bit data. General purpose register, BCDHL, these are the general purpose registers. Each register holds 8-bit of data. These registers can work in pair to hold 16-bit data and their pairing combination is like BC, DE and HL, program counter. It is an 16-bit register used to store the memory address location of the next instruction to be executed. Microprocessor increments the program 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. Flag pointer, it is a 16-bit register, works like stack which is always incremented or decremented by 2 during push and pop operations. Temporary register, it is an 8-bit register which holds temporary data of arithmetic and logical operations. Flag register, so there are 5 flags. These 5 flags are ordered by 8-bit flag register, sign, set, auxiliary carry, parity, carry flags. Depending on result, these are setting and resetting. So this is the sequence of flag, D0 holds carry, D1 don't care, D2 parity flag, D3 don't care, D4 auxiliary carry, D5 don't care, D6 zero flag, D7 sign flag. Pause the video and answer for this question. The question is how arithmetic and logical unit works. So it works on the basis of adder and subtractor circuit, performs addition, subtraction, multiplication, division. Instruction register and decoder, 8-bit register and an instruction is fetched from memory. Then it is stored in the instruction register. Instruction decoder decodes the information present in the instruction register. Timing and control, it provides timing and control signals to the microprocessor to perform operations. These are the timing and control signals like ready, read bar, write bar, ALE, S0, S1, hold, hold acknowledgement, reset in, reset out, etc. Interrupt control, there are 5 main hardware interrupts like RST 7.5, 6.5, 5.5 and trap. These 5 interrupts are managed by interrupt control unit. CDLIO controlled by SID and SOD for serial communication between microprocessor and external device. Address buffer and address data buffer holds address and either address or data respectively. Address bus and data bus, these carries address and data, 16-bit address, 8-bit data. These are the references. Thank you.