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ENGR 330: Today’s Class

ENGR 330: Today’s Class. Homework More LC-3 Assembly Language Revisit the Assembler Basic programming constructs Assignment 4. Homework Issues. Programming problems? Tool problems?. Revisit the Assembler.

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ENGR 330: Today’s Class

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  1. ENGR 330: Today’s Class • Homework • More LC-3 Assembly Language • Revisit the Assembler • Basic programming constructs • Assignment 4 R. Smith - University of St Thomas - Minnesota

  2. Homework Issues • Programming problems? • Tool problems? R. Smith - University of St Thomas - Minnesota

  3. Revisit the Assembler • Goal: produce a pattern of words to store in RAM, usually including machine instructions • Language has 3 parts • Instructions – 1 word each • Directives that adjust things • .ORIG to set starting address • .BLKW to set aside a block of words • .FILL to fill a word with a specific value • .END to mark the end • Labels – column 1 – stand for RAM addresses R. Smith - University of St Thomas - Minnesota

  4. Two Pass Assembly • Without it, you can’t do forward branches • WHY? • Because the first pass defines ALL RAM address labels • Pass 1 • Counts the number of words being assembled • One per instruction; one per .FILL • .BLKW may use many • Assigns values to RAM address labels • Pass 2 • Really translate the instructions into bit patterns • Convert RAM address labels to numbers as needed R. Smith - University of St Thomas - Minnesota

  5. Basic programming constructs • What to our classic languages provide • Java, C, Ada, Pascal, Basic, Visual Basic, etc. ? • Assignment statements • Arithmetic calculations • Conditional execution (IF statements) • Looping (Do, For, While, Repeat, ...) • We can do any of these, but we construct them out of multiple instructions R. Smith - University of St Thomas - Minnesota

  6. Assignment 4 • Add up a list of numbers • List is prefixed by a count of how many to add • Problem: how do we do a counting loop? • Leading decision vs trailing decision • Boundary conditions and condition codes R. Smith - University of St Thomas - Minnesota

  7. The Programming Process • Identify the details of the problem: what are the inputs, what are the results, what working storage do you need • Write out a list of computer steps to solve the problem – one step = the work of 1 or 2 instructions, no more or less • Translate each step into the actual instructions R. Smith - University of St Thomas - Minnesota

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