Difference between revisions of "CSC103: DT's Notes 1"
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When you have your circuit built, why don't you turn the power on and activate the two inputs (on the left) randomly, and when you are done, bring the two inputs back to 1 1, i.e. both red. Observe the output. Is it red? black? Anyhow, activate the inputs again, randomly, bringing them back to 1 1 (red red) at the end of your experiment. Chances are the output will be different from the last time you stopped. This is pretty amazing, if you think about it. We are using logic circuit, gates that implement the truth table of mathematically immutable laws, the laws of logic, but this circuit that we have built does not always output the same information, even when the two inputs are identical. | When you have your circuit built, why don't you turn the power on and activate the two inputs (on the left) randomly, and when you are done, bring the two inputs back to 1 1, i.e. both red. Observe the output. Is it red? black? Anyhow, activate the inputs again, randomly, bringing them back to 1 1 (red red) at the end of your experiment. Chances are the output will be different from the last time you stopped. This is pretty amazing, if you think about it. We are using logic circuit, gates that implement the truth table of mathematically immutable laws, the laws of logic, but this circuit that we have built does not always output the same information, even when the two inputs are identical. | ||
| + | Below is an image of the same circuit with a different output: | ||
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| + | <center>[[Image:CSC103FlipFlop2.jpg|600px]]</center> | ||
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| + | When you play some more with this circuit you will discover that what it does is remember which input is the last one you set to 0. If the last input that was 0 before you brought both of them back to 1 1 is the top input, then the output will be 1 (red). If the last input that was 0 is the bottom one, then the output will be 0 (black). | ||
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| + | This circuit has '''memory'''! That's magic. We are using purely combinational gates, gates that have no memory whatsoever in them, but by creating a loop (a figure 8 on its side, if you will) with the wiring, we create a feedback loop that helps information cycles around the loop. We won't study this more, as it is beyond the scope of our study, but if you are interested in this circuit, it is refer to in digital design as a ''flipflop''. The idea is that it behaves like a ''scale'' with two platters to weigh produce. The scale can be tilting left, or tilting right. That's the idea of a digital flipflop. | ||
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| + | <br /><center>[[Image:animatedScale.gif]]</center> | ||
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The memory is a collection of billions of memory words, each one storing a collection of bits. We saw earlier that a collection of bits can actually represents a binary number, and each binary number has an equivalent decimal number. So we can actually say that the memory is a collection of cells that contain numbers. It's easier for us human to deal with decimal numbers, so that's what we are going to do in the remainder of this section, but actually all the numbers in questions are binary. Makes sense? | The memory is a collection of billions of memory words, each one storing a collection of bits. We saw earlier that a collection of bits can actually represents a binary number, and each binary number has an equivalent decimal number. So we can actually say that the memory is a collection of cells that contain numbers. It's easier for us human to deal with decimal numbers, so that's what we are going to do in the remainder of this section, but actually all the numbers in questions are binary. Makes sense? | ||
Revision as of 08:57, 22 September 2013
--© D. Thiebaut 08:10, 30 January 2012 (EST)
