When the microprogram executes the End microinstruction of an instruction, then it generates the End control signal. This End control signal is used to load the PC with the starting address of fetch instruction ( In our case it is address 0 of microprogram memory). Now the CPU is ready to fetch the next instruction from main memory.

From the discussion, it is clear that microprograms are similar to computer program, but it is in one level lower, that's why it is called microprogram.

For each instruction of the instruction set of the CPU, we will have a microprogram.

While executing a computer program, we fetch instruction by instruction from main memory which is controlled by program counter(PC).

When we fetch an instruction from main memory, to execute that instruction , we execute the microprogram for that instruction. Microprograms are nothing but the collection of microinstrctions. These microinstructions will be fetched from microprogram memory one after another and its sequence is maintained by PC. Fetching of microinstruction basically provides the required control signal at that time instant.