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Isn't a digital signal an analog signal with a particular interpretation? I'm speaking of the static and dynamic disciplines for digital design. A digital log

by kmill 10y ago

Isn't a digital signal an analog signal with a particular interpretation? I'm speaking of the static and dynamic disciplines for digital design. A digital logic cell is an analog circuit with a nonlinear filter to bias the signal away from 0.5, ensuring interpretability, keeping noise from amplifying. And there are defined periods after a digital signal settles during which outputs are assumed not to have any valid digital interpretation. To nitpick: a digital circuit is always running (at the analog level) whether or not a clock pulse is hitting it. It's just that the digital circuit may begin to switch state when the clock signal is interpreted as a pulse. Then the analog transients eventually die out, which means everything has a digital interpretation, before the next pulse. Of course, none of this applies to an ideal digital circuit with every wire holding a perfect 0 or 1 signal. I think might be what you are talking about when you say "digital." I think if you used a genetic algorithm to produce digital circuits to model some function, you'd find it would use the logical gates well outside spec, taking advantage of intermediate states that we avoid by principle. In other words, sure it would use logical gates, but it would be an analog circuit.

nickpsecurity 10y ago
"Isn't a digital signal an analog signal with a particular interpretation?" Yes, technically. I love hitting people with that when they say digital "killed" analog. ;) What I'm getting at is that digital computers with digital cells and RTL operate in a way that simulates abstract operations on non-existent structures (bits) usually pretending to be on only periodically and requiring analog for real world interaction. The analog circuits, even Boolean alternatives, are closer to how the brain works as it's primitive components acting on real, physical values whose input and output mapping is more like a mathematical function. It similarly has precision and noise issues. "a digital circuit is always running (at the analog level) whether or not a clock pulse is hitting it" It's an abstraction issue. Digital is an abstraction over analog. At the digital level, it's not running since it's not performing the digital function or only partly. At analog level, it may or may not be running due to power management scheme. Clock gating basically. "I think if you used a genetic algorithm to produce digital circuits to model some function, you'd find it would use the logical gates well outside spec, taking advantage of intermediate states that we avoid by principle." Did you read that or were you really guessing? If the latter, it's a really good guess. I guessed that too given genetic programming results on antenna design. Our guesses were validated by various optimization techniques being applied to synthesis of analog circuits, including digital gates. Irritated I can't find the specific paper where they evolved cells or something but it used the opposite building blocks of human designers with better characteristics. Did find these, though. List of GP's evolved analog circuits that are human competitive in some way: http://www.genetic-programming.com/eh2004.pdf http://www.genetic-programming.com/eh2004.pdf ATLAS - simpler tool synthesizing individual, analog circuits http://www.ece.uc.edu/~dasan/iscas08.pdf http://www.ece.uc.edu/~dasan/iscas08.pdf Analog framework for fully-automated, standard cells and more http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-71.pdf http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-71... Note: Sorry I can't find the better stuff. Apparently, bio-tech, post-synthesis optimization, DNA computers, and analog synthesis of digital cells all use the exact, same words in their papers. Floods search results with garbage. Unreal. If you want, send me an email with subject like "synthesis of digital cell libraries" with a reminder to send you the paper if I run across it in future.

by kmill 10y ago

nickpsecurity 10y ago

"Isn't a digital signal an analog signal with a particular interpretation?" Yes, technically. I love hitting people with that when they say digital "killed" analog. ;) What I'm getting at is that digital computers with digital cells and RTL operate in a way that simulates abstract operations on non-existent structures (bits) usually pretending to be on only periodically and requiring analog for real world interaction. The analog circuits, even Boolean alternatives, are closer to how the brain works as it's primitive components acting on real, physical values whose input and output mapping is more like a mathematical function. It similarly has precision and noise issues. "a digital circuit is always running (at the analog level) whether or not a clock pulse is hitting it" It's an abstraction issue. Digital is an abstraction over analog. At the digital level, it's not running since it's not performing the digital function or only partly. At analog level, it may or may not be running due to power management scheme. Clock gating basically. "I think if you used a genetic algorithm to produce digital circuits to model some function, you'd find it would use the logical gates well outside spec, taking advantage of intermediate states that we avoid by principle." Did you read that or were you really guessing? If the latter, it's a really good guess. I guessed that too given genetic programming results on antenna design. Our guesses were validated by various optimization techniques being applied to synthesis of analog circuits, including digital gates. Irritated I can't find the specific paper where they evolved cells or something but it used the opposite building blocks of human designers with better characteristics. Did find these, though. List of GP's evolved analog circuits that are human competitive in some way: http://www.genetic-programming.com/eh2004.pdf http://www.genetic-programming.com/eh2004.pdf ATLAS - simpler tool synthesizing individual, analog circuits http://www.ece.uc.edu/~dasan/iscas08.pdf http://www.ece.uc.edu/~dasan/iscas08.pdf Analog framework for fully-automated, standard cells and more http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-71.pdf http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-71... Note: Sorry I can't find the better stuff. Apparently, bio-tech, post-synthesis optimization, DNA computers, and analog synthesis of digital cells all use the exact, same words in their papers. Floods search results with garbage. Unreal. If you want, send me an email with subject like "synthesis of digital cell libraries" with a reminder to send you the paper if I run across it in future.