Question 1: Four-Input Register (40 marks) There are two parts to this question. In the first part, you will design a register using 8 rising edge triggered D flip-flops. Use the template reg.circ file provided to design your register such that the input bits in_1 are copied onto the output bits out_1 when clock_1 is enabled. Name this circuit Sub_Register. In the second part, you will design a register using the Sub_Register circuit built in the first part. Begin by adding a new circuit to your project and name it Four_Input_Register. A copy of your sub-register from the first part will be used as a basis for this circuit. The register will have three input sources:

- an external data-in input - an 8-bit constant input initialized to zero, and - the output of an Adder that increments the register by adding 1 to the current value in the register.

Add a single clock bit to control the operation of the clock. Finally, add a multiplexer with 8 data bits and 2 select bits. Add a 2-bit input to connect to the select input of the multiplexer. The roles of the select bits are described in the table below. The operation is controlled by the clock input. S1 S0 Function 0 0 Load register from data-in input 0 1 Load register with constant 0 1 0 Increment the value in the register 1 1 Hold; Numbers in register are unchanged

A template file has been provided for you called reg.circ, which you can start with and then modify. You should not move the components given in the template. Explain your design in words in a separate (PDF) file, which you will upload, and then submit the circuit (reg.circ) implementation in logisim-evolution.