Register transfer operations enable data transfer between various blocks connected to the common bus of CPU. We have several registers inside CPU and it is needed to transfer information from one register another. As for example during memory write operation data from appropriate register must be moved to MDR.

Since the input output lines of all the register are connected to the common internal bus, we need appropriate input output gating. The input and output gates for register R_i are controlled by the signal R_{i in} and R_{i out} respectively.

Thus, when R_{i in} set to 1 the data available in the common bus is loaded into R_i . Similarly when, R_{i out} is set to 1, the contents of the register R_i are placed on the bus. To transfer data from one register to other register, we need to generate the appropriate register gating signal.

 For example,  to transfer the contents of register R₁ to register R₂, the following actions are needed:

• Enable the output gate of register R₁ by setting R_1out to 1.
              --  This places the contents of R₁ on the CPU bus.
• Enable the input gate of register R₂ by setting R_{2 in} to 1.
              --  This loads data from the CPU bus into the register R₂.