Here the data and the instructions are fetched internally and are sent to the processor directly within the processor. Different types of registers in microprocessors are as follow —. Program Counter Register holds the address of the next instruction to be fetched. Instruction is fetched from the address specified by the Program Counter PC. Once the instruction is fetched then the value with each operation PC increments its value.
The address specified by the PC first goes to another register known as memory address register. If CPU wants to write some data in memory then at which address this data will be written then this address is also specified by MAR. It means MAR simply stores the address from which CPU needs to fetch the instruction or data and also store the address where the data will be store in memory. Once the instruction is fetched from memory then fetched instruction is stored in Instruction Register, Decoder is connected with this instruction register and decode the fetched instruction.
This register is used for buffering of the memory so that instruction is not halted abruptly to the processor. When an instruction is decoded then we get the information about opcode, mode, and address field.
This address field provides the information either directly or indirectly about the address of the operand. When the operand address is found out the operand is fetched from that address and this operand is stored in a register known as memory data register. An accumulator is a type of registers that are used by CPU. This accumulator acts as a temporary storage location which holds an intermediate value in mathematical and logical calculations.
The second type of registers is important for computer architecture in enabling the accessibility to the instructions and fetch signals.
These registers are also known as general-purpose registers. It has a larger size as compared to the internal registers, hence these registers stores and perform operations larger than the internal registers. Despite being larger in size in terms of memory, these registers take a longer time than the taken usually by the internal registers in performing its operation. These registers include the Data register, responsible for temporarily storing the data being transmitted from one peripheral device to another.
An opcode represents the operation to be perform executed by the CPU. In Computer Architecture opcode is denoted in assembly language in mnemonic form. This opcode is also known as a command. The opcode is the ADD which represents that we addition of values stored in register R1 and register R2 should be performed.
The operand is the data on which the operation is going to be executed by the CPU. Aa in the above instruction Operands are the values stored in register R1 and register R2. Random-access Memory RAM. The main use of the memory data register is to act as a buffer as it can store anything that can be copied from the computer memory and can be used by the processor for further operations.
The memory data register stores the data before the data is transferred to the decoder. There are two types of registering in the memory data register. When the data is fetched from the memory and copied to the MDR the information is stored in one single direction and the data is written by other CPU registers that store data in computer memory.
The other use of the memory data register is to store the data and information that can be shifted to other memory components of the system or vice versa. The full form of MBR is the memory buffer register. The memory buffer register is used to store information and data that can be read or written in the computer memory. The main function of the memory buffer register is to store various types of computer instructions and data that can be transferred between computer memory.
The memory buffer register is the main memory-related register for the processor present in the processing unit as this register is capable to perform memory-related operations very fast. The full form of PC is the program counter register. The other name for the program counter register is instruction address register IAR or IC instruction counter. The program counter is used to indicate the current position of program sequence in a computer system. When any instructions are fetched from the memory the value of the program counter is incremented by one and point to next instruction that need to be executed by the processor of the central processing unit CPU.
The program counter is used to store the address of immediate instructions that need to be executed next. The processors in the CPU fetch the instructions sequentially but the sequence can be changed by other types of instructions like control transfer. The accumulator is another type of central processing unit register that is widely used for storing the logic or intermediate results. The accumulator register has a very important role as if it is not there then all the intermediate results need to be stored in the main memory that can increase the overhead on the memory.
It is because then unnecessary read and writes operations will be increased. The accumulator register can easily store the intermediate results.
The accessing speed of the accumulator register is much faster compared to the main memory. In many modern systems, there are various types of accumulators that can be used to store the intermediate results.
It keeps track of the the next memory address of the instruction that is to be executed once the execution of the current instruction is completed. In other words, it holds the address of the memory location of the next instruction when the current instruction is executed by the microprocessor.
This Register is used for storing the Results those are produced by the System. RAM , or the data after a fetch from the computer storage. It acts like a buffer and holds anything that is copied from the memory ready for the processor to use it. MDR hold the information before it goes to the decoder. MDR which contains the data to be written into or readout of the addressed location. For example, to retrieve the contents of cell , we would load the value in binary, of course into the MAR and perform a fetch operation.
When the operation is done, a copy of the contents of cell would be in the MDR. When the operation is completed the contents of cell 4 will have been set to 98, by discarding whatever was there previously.
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