Question

Question 4 2 pts Look at the following (incomplete) diagram of the Hack CPU. Look at the wire (and it is a single wire) pointed to by the large red arrovw Where does the signal on this wire come from and what action does this signal trigger? ALU output decode outM instruction inM addresSM reset PC Figure 5.9 Proposed CPU implementation. The diagram shows only data and address paths, namely, wires that carry data and addresses from one place to another. The dia not show the CPU's control logic, except for inputs and outputs of control bits, labeled with a circled "c". Thus it should be viewed as an incomplete chip diagram. gram does This is the "z" wire that comes out of the ALU. This tells the PC register whether to increment this time or stay the same This is the "z" wire that comes out of the ALU. This tells the PC register whether to increment this time or stay the same. The wire is load wire of the PC register. This tells the PC to load the value of the A-register. This wire comes from some logic gates that combines some status signals from the ALU with the three right-most (jump) wires of the C-instruction. This is the "inc" wire of the PC register. This wire tells the PC whether to increment or not. This wire comes from logic combining the values in the A-register with the ALU output to memory. This is "ignore reset" wire of the PC register. This wire tells the PC to ignore the signal that comes to the PC when the values of an A-instruction land in the A-register.

Answer 1

Here option b is correct. The reason is, program counter on each instruction either increment to next instruction address or jumps to other address when the branching condition is satisfied. So now if branching condition is satisfied then Program counter will increment to the address specified in the instruction and hence next address to move will come from A-register, otherwise it will simply increment to next address.

So this wire is load wire of program counter register which tells PC to load value of A-register if jump instruction is there.

Please comment for any clarification.