Question

The function table of a register with 2-bit control S1S0 is given below. The input to the i-th bit of the register is Bi, and the output of the i-th bit of the register is Ai. Assume this is a 4-bit register, and the input is B3B2B1B0=1101. Complete the table below assuming the value of A(t) are loaded after the i-th positive clock edge. (Bitwise OR means that each bit does an "OR" operation. i.e. A(t)=0011, B(t)=1000, then A(t+1) = 1011 )

Mode Control Register Operation Micro-operation
S1 SO
0 0 No change Ai(t+1) = Ai(t)
0 1 Bitwise complement Ai(t+1) = NOT(Ai(t))
1 0 Bitwise OR Ai(t+1) = Ai(t)+ Bi(t)
1 1 Parallel load Ai(t+1) = Bi(t)


1 0 1 2 3 4 5
S1S0 11
A(t) x

Answer 1

To complete the table, follow the control signal and perform micro-operations on the register bits. The completed table shows the values of A(t+1) for each state of the control signal.

Step-by-step explanation:

To complete the table, we need to follow the given control signal S1S0 and perform the corresponding micro-operations on the bits of the register. Let's start with the given input B3B2B1B0 = 1101:

1. For S1S0 = 11, the micro-operation is Parallel load. So, A3(t+1) = B3, A2(t+1) = B2, A1(t+1) = B1, and A0(t+1) = B0. Therefore, A(t+1) = 1101.
2. For S1S0 = 10, the micro-operation is Bitwise OR. So, A3(t+1) = A3 OR B3, A2(t+1) = A2 OR B2, A1(t+1) = A1 OR B1, and A0(t+1) = A0 OR B0. Using the previous value of A(t+1) = 1101, we have A(t+1) = 1101 OR 1101 = 1101.
3. For S1S0 = 01, the micro-operation is Bitwise complement. So, A3(t+1) = NOT(A3), A2(t+1) = NOT(A2), A1(t+1) = NOT(A1), and A0(t+1) = NOT(A0). Using the previous value of A(t+1) = 1101, we have A(t+1) = NOT(1101) = 0010.
4. For S1S0 = 00, the micro-operation is No change. So, A3(t+1) = A3, A2(t+1) = A2, A1(t+1) = A1, and A0(t+1) = A0. Using the previous value of A(t+1) = 0010, we have A(t+1) = 0010.

The completed table is as follows:

S1S0A(t)111101101101010010000010