Spring 2001 CSCI 255 Homework 4

You must show your work to receive full credit. This assignment is due Wednesday, 21 February.

Problem 1

Assume x is a C integer variable. Show how you would set bits 5, 7, and 9 of x to 1 and clear bits 11 and 13 to 0 in one C-statment.

Problem 2

Take the R-S latch in Figure 3.17 (p. 61) and replace the two NAND gates with two NOR gates. Show that the modified latch is stable if S, R, and a are all 0 while b is 1.

Now raise R to 1. What happens to your modified latch?

Finally lower R back to 0. Again, what happens to your modified latch?

Problem 3

Decode the following LC/2 binary instructions, specified as hexadecimal numbers. That is, determine the type (opcode) of each instruction and specify its fields:

• 0000
• 0246
• 1545
• 1FFF
• 4444
• 6666
• 8000
• 99BF
• BBBB
• F035