Found 475 Articles for 8085

Before having a discussion regarding the demerits or merits of I/O mapped I/O and memory-mapped I/O, let us have a generic discussion regarding the difference between I/O mapped I/O and memory 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 deviceOnly IN and OUT instructions are accessed by such devices.The ALU operations are not directly applicable to such Input-Output data.So as ... Read More

RST7.5 pin is an input which is edge-sensitive. Peripherals uses it for sending a pulse, rather than a sustained high level, for the interruption of the processor. Internal to 8085 we have a flip-flop which gets connected to the interrupt pin RST7.5. We set this flip-flop to 1, when a positive-going edge occurs on the input RST 7.5. The waveform of pin RST7.5 and output Q of RST7.5 flip-flop is shown in the Fig.Internal interrupt signal RST7.5 has a priority higher than the internal interrupt signals of RST6.5, RST5.5 and INTR. As we can see from fig the RST7.5 internal interrupt ... Read More

 Both the pins RST5.5 and RST6.5 pins are inputs which are level sensitive. RST6.5 is of higher priority than RST5.5 but the pin RST5.5 is of higher priority than INTR. RST5.5 and RST6.5 have similar functions. The point to be noted that these pins must remain high till the 8085 checks all the internal interrupt signals at the end of the instructions. As we can easily see from the Fig. We activate the RST5.5 and RST6.5 internal interrupt signals if and only if when the external interrupt pins are in logic 1 state;Flip-flop IE is in logic 1 state;SIM instructions ... Read More

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 More

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 More

The pins of Interrupt of 8085 are used by Input Output devices just for the initiation of the data transfer to or from 8085, without the wasting of the time of the CPU. As we have seen previously it is a very useful process when there is no well known Input Output timing characteristics, as it takes a very long time for getting ready of the device to perform the data transfer scheme. We have five interrupt pins of 8085 these are the input pins of 8085 which are named as TRAP, RST7.5, RST6.5, RST5.5 and INTR.The point to be ... Read More

We use this method when there is a lack of accurate knowledge of the timing characteristics of the Input Output device which takes maximum time for the device to be ready for use. Suppose we resort for the checking of data transfer; the processor here wastes a huge time in the loop for the device to get ready up to the mark. For avoiding this problem, we use the interrupt-driven data transfer process. Here the processor goes ahead with its desired work, and as soon as the device is ready for data transfer process, the corresponding Input Output port sends ... Read More

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