CMSC 311- Computer Organization

Fall 1995 - Assignment #6

Due (at the beginning of class) Thursday, November 2

1. Design a 4-bit register with the ability either to parallel load, to (bitwise) AND its parallel inputs with its current state, or to (bitwise) OR its parallel inputs with its current state. Your register should have two inputs, S1 and S2, to control its function. The function table for the register is given below:
```S0   S1   Function
0    0    Do Nothing
1    0    Parallel AND
1    1    Parallel OR
```
2. Design a circuit that performs a right circular shift of a four bit number by an arbitrary number of bits. Your circuit should have four input bits, four output bits and two control lines (S2, S1) that indicate the number of bit positions the input should be shifted (0, 1, 2, 3). The time to shift should not depend of the number of bits positions being shifted.
3. Design a combinational circuit that can compute any of the first eight of the logic operations (F0 thru F7) from Table 4-5 in Mano (page 110). Your circuit should have data inputs x and y, a single output z, and select inputs to determine which function is to be computed (how many select inputs do you need?). Show a circuit diagram.
4. From Mano, problem 4-17.
5. Given the initial state of Mano's computer shown below, trace through its execution, and show the memory, PC, and AC after each instruction has executed. Assume PC and AC are zero at the start.
```000   2009
001   7200
002   300B
003   200A
004   7200
005   000B
006   7200
007   300B
008   7001
009   0101
00A   1010
00B   0001
```
6. From Mano, problem 5-1.
7. From Mano, problem 5-4.