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Why does it take 5 machine cycles in the SHLD instruction of 8085 microprocessor?
fetch SHLD opcode bytefetch direct address least significant bytefetch direct address most significant bytewrite L register contents byte to memorywrite H register contents byte to memory
What is the use of NOP instruction in 8085?
The NOP (No Operation) instruction takes time but does nothing to the data or the status of the microprocessor. When executed in a loop, it can take substantial time, from microseconds, to milliseconds, to seconds.
What are registers in assembly language?
Registers are memory locations on the microprocessor itself (not in main memory). In RISC architectures generally most operations (add, multiply, etc) must take there input from registers and write their output to a register. Since registers are located directly on the microprocessor, they represent the fastest form of memory in the computer, and also the type of memory available in the least quantity.
What is the meaning of near and far definition in microprocessor programming using C?
Fundamentally any pointer in C is a reference to a memory location somewhere in system memory. While this seems simple in theory, in practice this is more complex when the microprocessor architecture is considered. Two considerations in computer programs are code size and speed. For this reason microprocessors have some additional modes which help reduce code and speed up code execution. Microprocessors fetch instructions from memory and then act on them. Included in these instructions are the addresses of the memory on which they will act. Modern microprocessors can access 2^32 memory locations (or more.) Thus a full memory location would take 32 bits to encode. The instruction may get quite large and take some moderate time to load from memory. To improve this situation the microprocessor manufacturers create instructions with "short" memory locations where part of the address is stored internally in a register in the microprocessor and the rest is held in this shortened address. These registers are called segment registers (in Intel processors) and the memory references are called relative addressing modes. This background finally brings us to the meaning of near and far. A near pointer reference is quick for the processor to handle but can only reference 64k bytes of memory. A far reference contains the entire memory location specified and can therefore specify memory anywhere in the microprocessor, it is however quite a bit slower to execute. This is less of an issue in modern processors but the choice becomes near and fast but only access 64k or far and slower but the entire memory map.
What is loop in microprocessor?
A loop in a microprocessor, like any loop in any programming language, is a series of instructions that is executed repeatedly until some condition is satisfied. An example of a delay loop in the 8085 might be... . PUSH FLAGS . XRA A L INR A . JNZ L . POP FLAGS This piece of code, with a 1 MHz clock, will take about 4.6 mS to execute, and it will save and restore the accumulator and flags.
Basic DMA operation and 8237 DMA Controller?
In the 8085, DMA (Direct Memory Access) is controlled with HOLD and HLDA. The HOLD signal is a request to release the bus. The HLDA signal is the 8085's acknowledgement of that request. HLDA means that the 8085 will release the bus in one half clock cycle, i.e. at the end of T3. The 8085 will remain in that hold state until HOLD is released, at which point it will take control of the buses again. The HOLD'ing device has complete control and can access any memory or I/O. Often, the 8237 DMA controller is used to provide sequencing of the operation. The 8237 DMA controller interfaces between up to four peripheral devices and the 8085. It provides an address register for each device so that the device does not need to do so. The device only needs to indicate that a byte of data is available, or is required, and the 8237 will take care of storing or fetching the byte.
Give over view of 8085 microprocessor?
The 8085 is an eight bit computer running on a 16 bit address bus. It has eight registers, A, B, C, D, E, H, L, and FLAGS, along with a 16 bit PC (Program Counter) and SP (Stack Pointer). Most intructions deal with eight bit values, but some deal with 16 bit values, and some registers can be paired to hold 16 bit values, such as BC, DE, and HL. The 8085 has multiple interrupt lines, INTR, RST5.5, RST6.5, RST7.5 and TRAP, and it can address 256 bytes of IO space. It has serial input (SID) and serial output (SOD) pins, but there is no implicit UART functionality built in. The 8085 has a READY pin which can be used to interface to slow memory, and a HOLD/HLDA set of pins that can be used to allow other bus masters to take over, such as in DMA operations.
If the frequency of the crystal connected to 8085 is 6MHz calculate the time to fetch and executed NOP instruction?
At a crystal frequency of 6MHz, the 8085 microprocessor has a clock frequency of 3MHz, or a period of 333 nanoseconds. The NOP instruction requires four clock cycles, three to fetch and one to execute, so the NOP instruction with a crystal frequency of 6MHz would take 1.333 microseconds to fetch and execute. This does not include wait states, each of which would add 0.333 microseconds to the timing.
Numerical and microprocessor relay comparison?
Numerical relays are all microprocessor based, but there are relays that take the advantage of microprocessor technology and are not fully numerical. In other words, if a relay is fully based on processing the samples of input signals it is numerical relay.
Specify the crystal frequency required for an 8085 system to operate at 1.1mhz?
The crystal frquency in an 8085 system is twice the desired clock frequency, so a crystal of 2.2 MHz is required to operate at 1.1 MHz.Note: Clock frequency is not the same as instructions per second, because the instructions in an 8085 take a variable number of clock cycles, between 4 and 18, to execute.
When was Take Your Memory with You created?
Take Your Memory with You was created on 1992-01-27.
What is the need for timing diagram in microprocessor?
The need for a timing diagram for a microprocessor is, primarily, to allow you to properly design the interface logic that will support the microprocessor. You need to know what lines are used to execute various data transfers, what are the timing of those lines with respect to each other, and how the microprocessor expects the external logic to behave. You can also use the timing diagram to understand how the microprocessor functions and, particularly, to know how long each instruction will take.
