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8085 Articles
Page 22 of 36
Comparison of memory-mapped I/O and I/O-mapped I/O
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 More8085 program to find minimum value of digit in the 8 bit number
In this program we will see how to find the minimum digit from a two-digit number.Problem StatementWrite 8085 Assembly language program to find the minimum digit from a two-digit number. The number is stored at location 8000H, store the result at 8050H.DiscussionHere we are performing this task by using masking operation. Each digit takes one nibbles. We are masking the upper nibble by ANDing with 0FH (0000 1111). Store the lower nibble into another register. After that, we are taking the upper nibble. To get it, we are shifting the number to the right four times to convert lower nibble ...
Read MoreData transfer schemes in 8085
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 More8085 program to reverse 16 bit number
In this program we will see how to reverse the digits of a 16-bit number using 8085.Problem StatementWrite 8085 Assembly language program to reverse a 16-bit number stored at location 8000H-8001H. Also, store the result at 8050H – 8051H.DiscussionHere the task is too simple. There are some rotating instructions in 8085. The RRC, RLC are used to rotate the Accumulator content to the right and left respectively without carry. We can use either RRC or RLC to perform this task. In the final result each digit of the H and L are reversed, and also the H and L values ...
Read MoreStatus check data transfer in 8085
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 More8085 program to show masking of lower and higher nibbles of 8-bit number
In this program we will see how to lower and upper nibbles are masked in 8085.Problem StatementWrite 8085 Assembly language program to mask the upper and lower nibble of an 8-bit number. The number is stored at location 8000H. Lower and Upper nibbles will be stored at location 8001H and 8002H.DiscussionThe masking is basically ANDing two numbers. When we want to mask the upper nibble of an 8-bit number say 2D (0010 1101), then we will AND with 0F (0000 1111), so we will get 0D (0000 1101). By masking with F0 (1111 0000), the result will be 20 (0010 ...
Read MoreReset_in* and Reset_out pins in 8085
Intel 8085 consists of a RESET_IN* pin which is an active low input pin. We RESET 8085 by placing a logic 0 on this pin at least for 0.5μs, after that the power is supplied to Vcc pin of 8085. Moreover, in practice we place the RESET_IN* in logic 0 state for a few milliseconds. A typical reset circuit which we use in ALS 8085 kit, is shown in the following Fig.The moment when the power supply is switched on, the Vcc pin gets +5V power here the RESET_IN* pin stays in logic 0 state for a time dependency on the ...
Read MoreAssembly program to transfer the status of switches
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 MoreAction taken by 8085 when INTR pin is activated
We have assumed that the interrupt system gets enabled by using the EI instruction, and the signals which have higher priority are not in active state.In the penultimate clock cycle of the last machine cycle of every instruction, the 8085 senses all the internal interrupt signals.If the INTR internal signal which is at logic 1, the 8085 enters to a machine cycle which is called interrupt acknowledge (INA) machine cycle.The interrupts from the Input Output port gets acknowledged by the 8085 by the activation of INTA* pin in the T2 state of the machine cycle INA where INTA* is a ...
Read MoreSubtract content of two ports by interfacing 8255 with 8085 microprocessor
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 ...
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