What Is a Processor Register?

The function of the register is to store binary code, which is composed of flip-flops with storage function. A flip-flop can store 1-bit binary code, so a register storing n-bit binary code needs to be constituted by n flip-flops. ^[1]

Register is

The register has at least the following four functions.

Clear digital: Clear the original digital in the register. ^[3]

In digital circuits, circuits used to store binary data or code are called registers. Registers are composed of flip-flops with storage functions. A flip-flop can store a 1-bit binary code, and a register storing the gate-bit binary code needs to be constituted by bamboo flip-flops. ^[4]

General register set

The general register group includes AX, BX, CX, and DX 4 16-bit registers to store 16-bit data or addresses. Can also be used as an 8-bit register. When used as 8-bit registers, they are recorded as AH, AL, BH, BL, CH, CL, DH, DL. Only 8-bit data can be stored, not the address. They are the upper eight bits and lower eight bits of AX, BX, CX, and DX, respectively. If AX = 1234H, then AH = 12H and AL = 34H. General-purpose registers are highly versatile, and they have the same function for any instruction. In order to reduce the length of the instruction code, in the 8086, some general-purpose registers are used for special purposes. For example, the CX register must be used as a count register in the string instruction to store the length of the string. This eliminates the need to specify the CX register number in the string operation instruction and shortens the length of the string operation instruction code. Here are one by one:

AX (AH, AL): Accumulator. Some instructions use AX (or AL) as the source or destination register. The input / output instructions must be implemented by AX or AL. For example, the instruction to read the contents of the port address 43H into the CPU is INAL, 43H or INAX, 43H. The destination operand can only be AL / AX, not other registers. ^[5]

In computers and other computing systems, a register is a very important and indispensable piece of digital circuit. It usually consists of flip-flops (D flip-flops) and is mainly used to temporarily store numbers or instructions. One trigger department stores one binary code. To store N binary numbers, N triggers are needed. ^[6]

(1) The code must be stored;

(2) Remember the code;

(3) Get the code. ^[7]

The ARM microprocessor has a total of 37 32-bit registers, of which 31 are general purpose registers and 6 are status registers. However, these registers cannot be accessed at the same time. The specific registers that can be accessed depend on the working state of the microprocessor and the specific operating mode. But at any time, the general registers R14 ~ R0, the program counter PC, and one or two status registers are accessible. ^[8]

Register addressing is to use the value in the register as the operand. This addressing method is a method often used by various types of microprocessors, and it is also a highly efficient addressing method. ^[10]

Register addressing means that the operand is stored in a register inside the CPU, and the instruction gives the name of the register in which the operand is located. Register operands can be 8-bit registers AH, AL, BH, BL, CH, CL, DH, DL, or 16-bit registers AX, BX, CX, DX, SP, BP, SI, DI, etc. Because register addressing does not require memory access via bus operations, instruction execution is faster. ^[11]

Register addressing (Register Addressing) is an addressing method that uses the contents of general-purpose registers as operands. In this addressing mode, the operands are stored in registers. The addressing objects of the register addressing mode are: A, B, DPTR, RO ~ R7. Among them, B is only for register addressing in multiply and divide instructions, and direct addressing in other instructions. A can be addressed by register or direct addressing. When direct addressing, A is written as ACC. ^[12]