CS270 Colorado State University

=========
LC3
=========
Ch 5

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Control Flow
    Typical fetch phase increments PC to address next instruction.
    
    Control flow instructions modify the PC.
    
    Example:

    0x3000  0xE0FF  [#R0 <- 0x3100]
    0x3001  0x0402  [#BR z +2]
    0x3002  0x103F  [#R0 <- R0 - 1]
    0x3003  0x0FFD  [#BR nzp -3]
    0x3004  0xF025  [#HALT]
    0x3100  0x000A  [#Data (1)]
    

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Addressing Modes & Wrap-up

      Immediate  Register  PC Offset  Indirect Base+Offset
ADD       X          X         -          -        -
AND
NOT
LD
ST
LDI
STI
LDR
STR
LEA
BR
JMP
JSR
JSRR
RET
RTI
TRAP

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LC3 Examples

  First Example:


  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  What does the program do?

  Will the program work?  If not, how can we fix it?

  Second Example:

























  
  The above example has a very strange method of operation, would it still work?

  What is the largest single value you could add with this method?

  Would this method work for negative numbers?


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LC3 debugging
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Ch 6

How can you run the simulator program in debug mode?

What makes debugging much easier?

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mstrout@cs.colostate.edu, 9/24/08  
pace@cs.colostate.edu, 9/29/08