![]() ![]() The "R" registers are meant for temporarily storage of values. The Accumulator alone would not be very useful if it were not for these "R" registers. Thus "R" registers are very important auxiliary or helper registers. To process the addition operation, execute the following command −Īfter executing this instruction, the accumulator will contain the value 30. Store a variable 10 in an accumulator and another variable 20 in, say, register R4. Consider an example of the sum of 10 and 20. These registers function as auxiliary or temporary storage registers in many operations. The "R" registers are a set of eight registers, namely, R0, R1 to R7. Access to main memory is slower than access to a register like the accumulator because the technology used for the large main memory is slower (but cheaper) than that used for a register. If the accumulator is not present, then every result of each calculation (addition, multiplication, shift, etc.) is to be stored into the main memory. The accumulator, register A, is used for all arithmetic and logic operations. We will discuss the following types of storage registers here − All these registers are of 8-bits, except DPTR and PC. The most widely used registers of the 8051 are A (accumulator), B, R0-R7, DPTR (data pointer), and PC (program counter). With 8-bit data type, any data type larger than 8-bits must be broken into 8-bit chunks before it is processed. ![]() In 8051, there is one data type is of 8-bits, from the MSB (most significant bit) D7 to the LSB (least significant bit) D0. Registers are used in the CPU to store information on temporarily basis which could be data to be processed, or an address pointing to the data which is to be fetched. ![]()
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