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exam1_2004 solutions

# exam1_2004 solutions - Department of Electrical and...

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Department of Electrical and Computer Engineering The University of Texas at Austin EE 306, Fall 2004 Exam 1 Solutions Yale N. Patt, Instructor Siddharth Balwani, Linda Bigelow, Tommy Buell, Jeremy Carrillo, Aamir Hasan, Danny Lynch, Rustam Miftakhutdinov, Veynu Narasiman, Vishal Parikh, Basit Sheikh, TAs 1) Part a) An instruction set generally consists of three kinds of instructions: _____ operates______ , an example of which is ___ ADD, AND, NOT ___ ___ data movement ___, an example of which is ___ LD, LDR, LDI, LEA, ST, STR, STI ___ ______ control ______, an example of which is ___ TRAP, JMP, BR, RTI, JSR ___ 1) Part b)If we can implement any logic function using many copies of a single gate (or a set of gates), then we say that single gate (or set of gates) is logically complete (or universal) 1) Part c)A ___ logical or boolean ___ variable is a variable that can have one of exactly two values. It gets its name from the fact that originally the two values were TRUE and FALSE, and the awareness that the value of such a variable must be exactly one of these two values. 1) Part d)If you know that R1 XOR R2 = 0, what can you infer about the contents of any of the registers R0 to R7? R1 and R2 must have the same values. Nothing about any of the others. 1) Part e)What logic structure does a mux with the 0 input line tied to the select line implement? Hint: Fill out the truth table. If you fill in the truth table, you will see that it is an AND gate. 2) Part a)The following LC-3 instruction is fetched, loaded into the IR, decoded, and executed. 0000 a b c 000000000 Note that bits [11:9] can each be 0 or 1. In ten words or fewer, what USEFUL

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information do bits a, b, and c provide in the execution of the particular 16-bit instruction shown above. Since adding 0 to the PC does not change the PC, the condition codes provide no useful information to THIS particular instruction, which is what the question asked. The hint: "Be careful" in boldface was supposed to help. Answer (in one word): NOTHING! 2) Part b) The LC-3 has just executed ten instructions. An examination of the behavior during each clock cycle reveals that exactly one of the ten instructions was a branch (opcode=0000) and the rest were some number of LDR, LD, and AND instructions.
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exam1_2004 solutions - Department of Electrical and...

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