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#1 RSC flip-flop question

Version 2.0
closed
nobody
None
5
2011-03-07
2010-10-30
Anonymous
No

Hello. Thanks for the awesome program, it really helps to understand the basics! I have a question with my 8bit reverse(bidirectional shift) register. I need to build it on RS flip flops and i get some troubles with different behavior of my own made RS and the library's one. I attached a file of my project, there are 2 main schemes, main and "main with native RS" and they are work different when it needs to shift loaded data in register. Native RS flipflop do it perfectly and mine doesnt work at all. I want to ask, how can i get the inside scheme of yours RS and compare with my to solve that problem. Thanks.

Discussion


  • Anonymous
    2010-10-30

     
    Attachments
  • Carl Burch
    Carl Burch
    2011-03-07

    I'm sorry I missed this when you posted it. I just noticed it.

    Internally, Logisim implements its built-in components using a behavioral description through Java code. Thus, the native RS flip-flop was not built with a correspondence to any particular circuit. Thus, as to how you can get into the schematic of the native RS flip-flop, the answer is simply that the schematic doesn't exist. (However, if you wanted to view the Java code, it is included in the downloaded JAR file (essentially a ZIP archive), in src/com/cburch/logisim/std/memory/SRFlipFlop.java .)

    The issue with your RS flip-flop is that it doesn't have an initial state - such a circuit has undefined initial behavior. My suggestion would be to introduce a "Reset" input to your RS flip-flop, which would be wired as a third input into the lower right NOR gate. It then wouldn't "default" to 0 like the built-in RS flip-flop, but you could easily tell all flip-flops to reset by giving this as an input.

     
  • Carl Burch
    Carl Burch
    2011-03-07

    • status: open --> closed