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Microcontroller Articles
Page 23 of 33
8086 program to transfer a block of 4 bytes by using string instructions
In this program we will see how to transfer a 4-byte block from one location to another location.Problem StatementWrite 8086 Assembly language program to transfer a four-byte block from one memory section to another memory section. The numbers are stored at memory offset 500 – 503.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 one location to another. As the ...
Read MoreComparison 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 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 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 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 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 MoreRST5.5 and RST6.5 pins in 8085
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 MoreRST7.5 pin in 8085
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 MoreTrap interrupt pin in 8085
A non-maskable interrupt is a Trap Interrupt which implies that whenever this pin gets activated, the 8085 always gets interrupted even if the state of 8085 is in DI. The input of Trap input is level sensitive and edge sensitive. Hence the Trap line always makes a transition from 0 to 1, and remains in state 1 until the end of the execution of an instruction for the interruption of 8085. A vectored-interrupt in 8085 is a TRAP. The starting address of 8085 is known by itself the of the ISS as 4.5 * 8 = 0024H. Hence we name the ...
Read MoreNeed for masking in 8085
Let us say that the 8085 which is interrupted because of RST6.5 pin and has been branched to the ISS for the pin RST6.5. Then, except the DI instruction at the beginning of this ISS, all the interrupts gets disabled except TRAP. So, even if RST7.5 pin is in activated state in the middle of the execution of RST6.5 ISS, the interruption of 8085 will not occur due to RST7.5. Actually a higher priority interrupt is RST7.5, but the lower priority interrupt ISS cannot be interrupted by it of RST6.5. We solve this problem by specifically having the instruction which ...
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