University of Illinois at Urbana Champaign 1Using LogicWorksCelal ZiftciCS 231 – Fall 2005Sep 9, 2005University of Illinois at Urbana Champaign 2Reminders Homework #1 due Monday, Sep 12 Check the website for office hours?(no changes, but still…)University of Illinois at Urbana Champaign 3What is LogicWorks? A software that allows simulation of hardware components and their interactions. Advantages of using a simulator Cost TimeUniversity of Illinois at Urbana Champaign 4Important… Even if you are working in groups on the MPs (not HWs), use it for some time Be neat and organized! Use labels on pins, instead of crossing wires everywhere Typically, data flows from left to right.(Except in our datapath, where it flowsup Æ down Æ up)University of Illinois at Urbana Champaign 5Today’s outline Interface Working with devices Input and output DebuggingUniversity of Illinois at Urbana Champaign 6Interface Main layout screen Parts of list palette (can tear off) Simulation Gates: and, or, not, ... Simulation IO: binary switch, hex keyboard, binary probe, hex display Simulation Logic: adder, clock, flip-flop, decoder, mux double click device in parts palette single click in layout to place deviceUniversity of Illinois at Urbana Champaign 7Interface (2) Timing diagram Can be accessed underView ÆTiming Window For sequential circuits (MP3 & 4) Shows clock and signals over time Zoom in and out using toolbarUniversity of Illinois at Urbana Champaign 8Interface (3) Drawing Toolbar Zap to delete lines & components - useful to cleanup mistakes Text tool to add labels and pin names Signal wire (1-bit) Bus wire (multi-bit)University of Illinois at Urbana Champaign 9Interface (4) Simulation Toolbar For sequential circuits (MP3 & 4) Adjust simulator clock speed As alternative to using a fixed clock speed, use binary switch as "clock" and manually toggle when a clock cycle happens. Easier to verify that everything happened correctly.University of Illinois at Urbana Champaign 10Interface (5) File menu Open... Type: Circuits files Type: Symbol libraries (to be used later)University of Illinois at Urbana Champaign 11Interface (6) Schematic menu Design Preferences Show printed page breaksMake sure components don't span page breaks Show background gridUniversity of Illinois at Urbana Champaign 12Interface (7) Keyboard shortcuts Arrows make gate point left, right, up, or down Context menu (right click) Name: useful to label components in big circuits Right click tip of pin Name: to connect pins without drawing a wireUniversity of Illinois at Urbana Champaign 13Working with devices Connecting devices Naming the pins reduces the mess Drag wire from one pin to another Use signal or bus tool Ends must contact — intersect is not enough! Entire wire & pins should turn yellow when selectedUniversity of Illinois at Urbana Champaign 14Working with devices (2) Be careful using gates with inverters Making gates with more inputs Append the gates to each other Use some logic BUT be careful on the implications E.g. AND-6: a six input AND gate Use AND-8 — What to do with remaining pins? E.g. AND-6 Use AND-3 plus AND-4 — How to connect? Don't use five AND-2 gates!University of Illinois at Urbana Champaign 15Input and Output Binary switch Enter 1 bit To move switches (and most of the other components too) hold down shift while clicking Binary probe Display 1 bit. Really useful for debugging! Z: unknown value — somewhere a pin is disconnected C: conflict value — 2 conflicting pins with same label Sometimes just need to toggle inputsUniversity of Illinois at Urbana Champaign 16Input and Output (2) Hex keyboard Enter 4 bits in hex — useful for our 4 bit bus Lowest pin, by F, is lower order bit 0 Observe it for yourself. How? (Hint: Probe) Hex display Display 4 bits in hex 7 segment display (LED) Gray if unknown — this indicates a bug! Blank (white) if 0 Solid black(or red) if 1University of Illinois at Urbana Champaign 17Debugging Use lots of binary probes Verify that pins are connected Remember yellow Verify that correct pin names are used (spelling,
View Full Document