The interrupts in 8085 is classified into the following partsThe data transfer scheme: Executing of 8085 program where the communication process is carried out systematically and is not done directly with the Input Output device. The data transfer can be either in two forms namely parallel or serial respectively.Basic or simple data transfer scheme: The simplest data transfer scheme is the basic or simple data transfer. This method is beneficial to us when we have accurate know-ledge of the Input Output device timing characteristics.Status check data transfer: Status check data transfer process is a much more complex process than simple data transfer. We ... Read More

In Memory Mapped Input Output −We allocate a memory address to an Input-Output device.Any instructions related to memory can be accessed by this Input-Output device.The Input-Output device data are also given to the Arithmetic Logical Unit.Input-Output Mapped Input Output −We give an Input-Output address to an Input-Output device.Only IN and OUT instructions are accessed by such devices.The ALU operations are not directly applicable to such Input-Output data.So as a summary we can mention that −I/O is any general-purpose port used by processor/controller to handle peripherals connected to it.I/O mapped I/Os have a separate address space from the memory. So, total ... Read More

Generally, a processor like 8085, to address one I/O port by sending out 8-bit port address and IO/M* = 1. For example, let us say, the chip select pin of an I/O port chip is activated when 8-bit address = F0H, IO/M* = 1, and RD* = 0. This is shown in the following fig.Such I/O ports, which are addressed by the processor by sending out IO/M* as logic 1 are called I/O-mapped I/O ports.An Input Output port is generally addressed by 8085 Processor by releasing the port address of 8-bit and IO/M* = 1. An example to be cited ... Read More

It is possible to address an I/O port as if it were a memory location. For example, let us say, the chip select pin of an I/O port chip is activated when address = FFF0H, IO/M* = 0, and RD* = 0. This is shown in the following fig.In this case, the I/O port chip is selected when the 8085 is thinking that it is addressing memory location FFF0H for a read operation. Note that 8085 thinks that it is addressing a memory location because it has sent out IO/M* as a logic 0. But in reality, an input port ... Read More

The Central Processing Unit and the main memory are always very accurate and fast as compared with electromechanical input or output devices like printers, etc. Here in this case it is essential for us that the data lines of the computer are not engaged for a long time during communication process with input/output devices. Else the overall speed of the computer system drastically falls below. So the Input Output devices gets connected to a computer through the Input Output ports. Two Instructions are fetched which are called as IN and OUT where there are 256 Input Ports and 256 Output ... Read More

In this program we will see how to perform subtraction by using ports to take data and send the result into the port.Problem StatementWrite 8085 Assembly language program for interfacing between 8085 and 8255. Here Port A and Port B are holding two values, take the numbers from port A and B, subtract B from A, and send the result at port C.DiscussionThe task is very simple. At first we have to setup the control word register of 8255 chip. After that we will take the input from port A and B, add the content, and send it to port ... Read More

Microprocessors and microcontrollers can be used to design some tools or systems to perform some special tasks. Using microcontrollers, we can make different types of modules or systems. Here is a list of some systems that can be designed by using microcontrollers −Electronic Voting MachineRFID based Access Control SystemHeart Rate monitoring systemAutomatic Plant watering systemUltrasonic range finding systemWater level controlling systemGas leakage detection systemFrequency MetersTemperature measuring systemThere are many such systems that can be made by using some microcontrollers.To design a system, we have to follow some basic steps. We have to design the overview of the system, and some ... Read More

In this section we will see how to reset the accumulator content in Intel 8085 and 8086 microprocessors.In both of the microprocessors, there are four instructions to do the work. These instructions are doing the same in both cases.Let us see the 8085 instructions first to reset the Accumulator.MnemonicsDescriptionMVI A, 00HThis instruction loads 00H into the accumulator. This is two-byte instruction.ANI 00HThis instruction performs AND operation between accumulator and 00H. This is also a two-byte instruction.XRA AThis one-byte instruction is performing the XOR operation with accumulator itself.SUB ASUB A is another one-byte instruction. It subtracts accumulator value from the accumulator. The ... Read More

A microprocessor is an integrated circuit which can function as a central processing unit (CPU) of a computer system or a microcontroller. It is constructed by integrating millions of transistors, diodes, and resistors on a single electronic chip.8085 and 8086 are two major types of microprocessors produced by Intel. Go through this article to find out the major differences between 8085 and 8086 microprocessors.What is 8085 Microprocessor?The 8085 microprocessor is an 8-bit microprocessor produced by Intel in 1976. The 8085 microprocessor has 8-bit long data bus, thus it can process 8-bit of data in a single cycle. The 8085 microprocessor ... Read More

In this program we will see how to transfer the switch values from one port to another using 8085 and 8255 chip.Problem Statement:Write 8085 Assembly language program for interfacing between 8085 and 8255. Here eight switches are connected at port A. Transfer the status of these switches into port B. In port B the LEDs are connected.Discussion:The task is very simple. At first we have to setup the control word register of 8255 chip. After that we will take the input from port A, and send it to port B.The control word register is looks like this. It is holding ... Read More