| # Universal gates, self-documenting version |
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| This project is an enhanced version of [unigate-gf](https://github.com/htfab/unigate-gf). |
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| In <i>normal</i> mode, it contains four independent universal logic gates: |
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| - <i>U</i><sub>21</sub> on input pins 5-8 and output pin 32 |
| - <i>U</i><sub>31</sub> on input pins 9-14 and output pin 33 |
| - <i>U</i><sub>41</sub> on input pins 15-24 and output pin 34 |
| - <i>U</i><sub>22</sub> on input pins 25-30 and output pins 35-36 |
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| where <i>U<sub>ij</sub></i> can be suitably wired to power, ground and inputs such that |
| it implements any particular Boolean function on <i>i</i> inputs and <i>j</i> outputs. |
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| There is an additional mux that selects one of the outputs of the above <i>U</i><sub>22</sub> |
| based on input pin 31 and outputs it on pin 37. This allows us to transform <i>U</i><sub>22</sub> |
| into another instance of <i>U</i><sub>31</sub>. |
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| In <i>reference</i> mode, it uses a lookup table to tell us how to wire the universal gates to |
| achieve a specific Boolean function. |
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| - setting input pins 5-6 and 31 and clearing input pins 7-8 activates reference mode |
| (this particular combination is never needed in normal mode) |
| - use input pins 9-10 to select one of <i>U</i><sub>21</sub>, |
| <i>U</i><sub>31</sub>, <i>U</i><sub>41</sub>, <i>U</i><sub>22</sub> |
| - use input pins 11-26 to specify the truth table of the Boolean function |
| - use input pins 27-30 to specify the input pin number to be wired |
| - signal on output pin 32 means the selected pin should be wired to ground |
| - signal on output pin 33 means the selected pin should be wired to power |
| - signal on output pins 34-37 mean the selected pin should be wired to |
| the inputs 1-4 of the Boolean function respectively |
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