moonlit Posted November 8, 2003 Share Posted November 8, 2003 I'm having a difficult time understanding LC-3 instructions and registers. Can someone help me with these few problems, maybe explain them step by step. Thanks! 1) What is the difference between the following LC-3 instructions A and B? How are they similar and how are they different? A: 0000111101010101 B: 0100111101010101 2) The LC-3 does not have an opcode for the logical function OR. That is, there is no instruction in the LC-3 ISA that performs the OR operation. However, we can write a sequence of instructions to implement the OR operation. THe four instruction sequence below performs the OR of the contents of register 1 and register 2 and puts the results in register 3. Fill in the two missing instructions so that the four instruction sequence will do the job: (1): 1001 100 001 111111 (2): (3): 0101 110 100 000 101 (4): 3) The PC contains x3010. The following memory locations contain values as shown: x3050 x70A4 x70A2 x70A3 x70A3 xFFFF x70A4 x123B The following three LC-3 instructions are then executed, causing a value to be loaded into R6. What is the value? x3010: 1110 1110 0011 0001 x3011: 0110 1000 1100 0000 x3012: 0110 1101 0000 0000 We could replace the three-instruction sequence with a single instruction. What is it? 4) It is the case that we REALLY do not need to have load indirect (1010) and store indirect (1011) instructions. We can accomplish the same results using other instruction sequences instead of using these instructions. Replace the store indirect (1011) instruction in the code below with whatever instructions are necessary to perform the same function: x3000: 0010 0000 0000 0010 x3001: 1011 0000 0000 0010 x3002: 1111 0000 0010 0101 x3003: 0000 0000 0100 1000 x3004: 1111 0011 1111 1111 Link to comment Share on other sites More sharing options...
bigjnorman Posted November 10, 2003 Share Posted November 10, 2003 perhaps if you gave us the instructions in a different format, seeing the opcodes mean nothing to me as I have never used LC-3, so I would need an entire list of opcodes & corresponding instructions to see what you are trying to do. ex) ADD R1,R1,R3 ADD R1,R1,#3 LD R6,NUMBER Link to comment Share on other sites More sharing options...
moonlit Posted November 10, 2003 Author Share Posted November 10, 2003 Here's a link to the ISA of the LC-3... http://highered.mcgraw-hill.com/sites/dl/free/0072467509/104653/PattPatelAppA.pdf Link to comment Share on other sites More sharing options...
bigjnorman Posted November 13, 2003 Share Posted November 13, 2003 I have no idea, i've only had a little bit of assembly back in Comp. Architecture and we used a MUCH simpler platform Link to comment Share on other sites More sharing options...
moonlit Posted November 13, 2003 Author Share Posted November 13, 2003 It's ok...I've got some answers figured out. Thanks anyway. Link to comment Share on other sites More sharing options...
apollo2011 Posted December 11, 2003 Share Posted December 11, 2003 I think I should know this but... what is LC-3? Link to comment Share on other sites More sharing options...
Guest asdasdasdasd Posted June 14, 2004 Share Posted June 14, 2004 Hey moon lit do u still have the answers to those questions. I would like to know them. just e-mail me Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now