Arithmetic Micro-Operations

Micro-operations are operations done on data contained in registers. A micro-operation is a simple operation performed on data stored in one or more registers.

Addition, subtraction, increment and decrement are examples of micro-operations. Let us understand arithmetic micro-operations with examples. 

Add Micro-Operation

The following phrase summarises it:

R1 + R2 = R3

The information or contents of register R1 are to be placed into the data or contents of register R2, and the total is to be translated to register R3.

Subtract Micro-Operation

Subtract micro-operations are comparable to R3 → R1 + R2′ + 1 because they use the minus operator to construct 1’s complement and add 1 to the register that is subtracted.

Increment/Decrement Micro-Operation

It is commonly implemented by adding and removing 1 from the register, accordingly.

R1 → R1 + 1

R1 → R1 – 1 

Plus one and minus one operations represent increment and decrement micro-operations, respectively. A binary up-down counter or a combinational circuit is used to conduct these micro-operations.

The table does not include the arithmetic operations of multiply and divide. These two arithmetic operations are valid, although they are not included in the basic set of micro-operations.

In this case, the signals that execute these operations pass via gates, and the operation’s result can be transmitted into a destination location via a clock pulse shortly after the output signal passes through the combinational circuit.

A series of add and shift micro-operations are used to perform the multiplication operation. A series of subtracting and shifting micro-operations are used to complete the division.

Arithmetic Logic Shift Unit in computer architecture

In a computer system, the Arithmetic Logic Shift Unit (ALSU) is a component of the Arithmetic Logic Unit (ALU). It is a logical, arithmetic, and shift-based digital circuit. Rather than having individual registers calculate micro-operations individually, the computer uses a group of storage registers linked to a common operational unit called an arithmetic logic unit, or ALU.

The contents of specified registers are now allocated in the inputs of the shared ALU to implement the micro-operation. The ALU performs a result-oriented action that is transmitted to a destination register. The ALU is a combinatory circuit that performs the entire register transfer operation from the supplier registers to the destination register in a single clock pulse amount. The shift micro-operations are often conducted in a separate unit, but they are also made as part of the entire ALU.

By combining arithmetic, logic, and shift circuits, we can create a single ALU with shared selection variables. In the diagram below, we can observe the first level of an arithmetic logic shift unit. The inputs S1 and S0 are used to choose specific micro-processes.

At the output, a 4 x 1 multiplexer selects between an associated arithmetic output in Ei and a logic output in Hi. Inputs S3 and S2 choose the data in the multiplexer, and the other two data inputs in the multiplexer receive the inputs Ai – 1 for the shr operation and Ai + 1 for the shl operation.

Note: A specified arithmetic stage’s output carry Ci + 1 must be connected to the input carry Ci of the next stage in the sequence.

Conclusion

Micro-operations are operations performed on data stored in registers. Shift, count, clear, increment, load and other basic operations are done on information stored in registers. Arithmetic micro-operations diagrams are operations done on numeric data contained in the registers in general. The following are the categories of basic arithmetic micro-operations, namely, subtraction, addition and increment.

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