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Join Date: Mar 2009
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Need help with LC-3 rotate bit pattern program
Requirements,
A program that rotates a bit pattern to the left by a certain amount, (again a number between 0 and 16, including 0 and 16). The bit pattern is found in location x3100 with the rotate amount in memory location x3101. As before, the result is to be placed in location x3102. The program starts at location x3000. The difference between a rotate and a shift is that the bits that would have been lost in the shift are 'wrapped' around and moved into the right side of the pattern. For example, if the original pattern is 1101000100001011 and the rotate amount is 0000000000001100 (decimal 12), the result in x3102 should be, 1011110100010000. Here is what I have so far, 0011 0000 0000 0000 ; program starts at location x3000 0010 001 100000000 ; load bit pattern to left rotate 0010 010 100000001 ; load number of times to rotate 0000 010 000001011 ; branch to done if count is 0 0101 011 011 1 00000 ; clear r3 0001 001 001 1 00000 ; set condition code based on value in r1 0000 011 000000111 ; branch if positive or zero 0001 011 011 1 00001 ; most significant bit is 1 0001 001 001 000 001 ; left shift by one 0001 001 001 000 011 ; add back in shifted out bit 0001 010 010 1 11111 ; decrement count 0000 111 000000010 ; branch to top of loop 0011 001 100000010 ; store shifted result 1111 0000 00100101 ; halt the simulator Then this is my actual code but I need help finishing it. ST LD, R1, NOT SURE WHAT GOES HERE LD, R2, NOT SURE WHAT GOES HERE BRz DONE ADD R3,R3, #0 ADD R1,R1, ....NOT SURE WHAT TO PUT HERE BRzp ???? ADD R3,R3,#1 ADD R1,R1,#1 ADD R1,R1,#3 ADD R2,R2, ? BRnzp ??? ST R1 ?? TRAP x25 |
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