A decoder is required in case of a Vertical Microinstruction because it helps in the execution of the microinstruction. Let's understand the concept of a decoder and microinstructions in detail.

Microinstructions are low-level instructions that control the operation of a microprogram, which is a set of microinstructions stored in control memory. These microinstructions are executed by a microprocessor to perform various tasks.

A microinstruction consists of several fields, including the opcode field, which specifies the operation to be performed, and the address field, which specifies the address of the next microinstruction to be executed. The opcode field is decoded to determine the operation to be performed.

A decoder is a combinational logic circuit that takes a binary input and produces a specific output based on the input value. In the case of microinstructions, a decoder is used to decode the opcode field of the microinstruction.

Now, let's discuss why a decoder is required in the case of a Vertical Microinstruction.

Vertical Microinstruction:
A vertical microinstruction is a type of microinstruction format where each bit position in the opcode field corresponds to a specific control signal. In other words, each bit of the opcode field directly controls a specific part of the microprocessor.

A decoder is required in the case of a Vertical Microinstruction because it helps in decoding the opcode field and generating the control signals required for the execution of the microinstruction. The decoder takes the binary value of the opcode field as input and produces the corresponding control signals as output.

The control signals generated by the decoder are used to control various parts of the microprocessor, such as the ALU (Arithmetic Logic Unit), registers, memory, etc. These control signals determine how the microinstruction is executed and what operations are performed.

By using a decoder in the case of a Vertical Microinstruction, the microprocessor can efficiently execute the microinstruction by generating the required control signals based on the opcode field. This allows for a more streamlined and organized execution of microinstructions, leading to improved performance and functionality of the microprocessor.