 For this example, we're going to pretend as though we're the control unit, and we're going to be interested in setting all of these control lines to their applicable values based on the instruction that we want to execute. For this first example, we're just going to start with an add instruction. And we'll work our way across this table, setting each of the bits as we go. For the add instruction, we want to take the data from two registers, add it together, and store it back into a register. So first, for our ALU source, we want to be able to get the data from our second register, so we're going to set this control line to zero. That will go through the ALU and back around to the registers, ultimately. Since we do want to write this result to the registers, we'll set reg write to one. That will tell the registers to store whatever data we give it. Now we need to make sure we actually give it the correct data. So the mem to reg multiplexer allows us to choose between the results of our ALU and whatever data we're reading out of memory. Since we want to store the results of our addition operation, we'd like to take this data coming from the ALU. In this case, that also says zero, so I will put a zero in for that signal. Now the data will come around to the write data field in our registers. But we also need to tell the machine which register we should store this into. When we have two different options, we can either use what's coming in on the RT field or the RD field. In this case, we have an R-type instruction, so we know our destination is always in the RD field. So that means I will want to set my reg destination signal to one. The rest of our signals are very instruction dependent. In this case, we don't have a memory read instruction. So we're not going to read anything from memory. We don't have a memory write instruction, so we're not going to write anything to memory. We don't have a branch instruction, so we're not going to branch. And we don't have a jump instruction, so we're not going to use the jump. So those are the eight main signals that we have to worry about. We need to configure each of our multiplexers and make sure that any of our functional units know what they need to do as well.