Status check data transfer process is a much more complex process than simple data transfer. We use this method is used when there is lack of accurate knowledge of the Input Output device consisting of the timing characteristics. Status information is received by the processor regarding the readiness of the Input Output device for performing the data transfer. Generally, the processor is involved in the checking of the loop for the device to get ready. The device releases from the loop when the device is ready for use for the execution of the IN or OUT instruction which depends on ... Read More

 The simplest data transfer scheme is the basic or simple data transfer. This method is beneficial to us when we have accurate knowledge of the Input-Output device timing characteristics. When we become familiar that the device is ready for transferring data, we execute the instructions IN and OUT, depending on the required data transfer direction. In this case when the Input Output port gets connected in the system as an I/O-mapped I/O port. If we connect the port as a memory-mapped I/O port, “MOV M, A”, “MOV A, M”, or any other memory reference instruction is used which depends on ... Read More

At the time of executing one 8085 program, interruption can be done in the mid-way by the virtue of the program by an Input Output device. Interruption can be done by the method according to which the processor works, since it wants urgent communication with the processor. The data transfer schemes always want for sending information to the processor, rather receiving information from the 8085 processor. It is so because sending and receiving information in the entire 8085 data transfer scheme process plays a vital role for executing the entire program rather process.The communication is not done directly with the ... Read More

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

In this program we will see how to find a number n from a string (an array of numbers).Problem StatementWrite 8086 Assembly language program to find a number in a string (an array of numbers). The numbers are stored at memory offset 600 onwards.DiscussionIn this program we are taking only 5 numbers. We are searching the number 25. after successful search the DX register will hold the offset address, and BX register will hold the index of that number.We are taking each number from that array and then compare it with 25. If the numbers are same, then we will ... 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

The 8255 is a general purpose programmable IO device. It is designed to interface the CPU with some external devices like ADC, DAC, keyboard etc. We can program the device according to the given condition.There are three 8-bit bi-directional IO ports. The Port-A, Port-B, and Port-C. These ports are assigned as input or output port.The block diagram of 8255 is like this:There are two different modes of 8255. These modes are:Bit Set Reset (BSR) ModeInput/ Output ModeBit Set Reset (BSR) ModeThis mode is used to set or reset the bits of the Port-C only. For BSR mode always D7 will ... Read More

In this program we will see how to transfer a block from one location to another location.Problem StatementWrite 8086 Assembly language program to transfer a block from one memory section to another memory section. The numbers are stored at memory offset 501 onwards. The block size is stored at memory offset 500.DiscussionHere we are initially setting up the source index register with the source of data blocks, then set the destination index register to store into another block. Then set the Data segment register and Extra Segment register to 0000H. By using MOVSB instruction, the entire block is transferred from ... 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