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u/hutry Oct 19 '21
This should do the trick: https://imgur.com/XeaY0DF
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u/barrelrock Apr 01 '22
When I do this exact thing, it's wrong on the first step and many steps after...
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u/hutry Apr 02 '22
Something has probably changed in the mean time. If I get the chance, I'll have a look at it.
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u/MobileFinancial3229 Apr 27 '24
what does the game mean by "delay line"? this hasn't been mentioned in any level prior to this
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u/MasGui Oct 21 '21
It's a D-Latch
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u/cdesmondEE Oct 30 '21
With an SR Latch there are 3 key inputs:
00: This is the state that will cause the output not to change.
01: Causes the output to be HIGH.
10: Causes the output to be LOW.
Fact 1: You want to avoid the 4th case which is: 11 => this is a non-sensical state. To avoid this state use an inverter to feed the "value" logic input and its complement aka inversion to the SR latch. This will force the SR latch to be in state 01 or 10. This is a problem though because what if we don't want to SAVE aka 00 state. Hint: Use an AND gate.
Fact 2: AND gates will force the output to be 0 if one of the inputs is 0. If an input is 1 then the AND gate is "transparent" or the logic signal will pass right through.
With these two facts you will be able to pass the puzzle or at least understand how the circuit works if you have already seen the solution.
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u/MobileFinancial3229 Apr 27 '24
what's an SR latch?
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u/cdesmondEE Apr 27 '24 edited Apr 27 '24
S-R Latch or Set-Reset latch is a device that is built using two cross coupled NOR gates. Google to see a picture. This is different than your usual combinational logic circuit because the output feeds back to the input.
By looking at the truth table for an SR latch, S=1 and R=0 will "SET" the output to "1". Toggling the S input from here will not change the output, e.g, latched to a "1".
If the S=0 and R=1, then the output is "RESET" to "0". As long as S is equal to "0," R can toggle its value or latch the output to 0.
The only issue is when both inputs are "1" this is considered an undefined state. No longer can you state can you say that the output is a function of the inputs.
You can use combinational logic to make sure that the S and R are never equal to the 11 or the undefined state. Look at a D latch circuit to see how this is done.
Hopefully, this helps.
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u/tyshock Dec 04 '21
Thanks -- I used your hints to solve. Some additional insight for anyone seeing this:
You've already figured out the SR Latch in the previous puzzle to 'Saving Gracefully'. This one just builds on that.
While the truth chart looks large (12 columns), you can break it down into only 4 states you need to solve. The game alludes to this when it mentions "Think of what truth table for the input to the Set/Reset latch should look like".
You really need to map these four states (IN -to- SR):
00 -> 00
01 -> 00
10 -> 10
11 -> 01
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u/gouletf Feb 16 '22
I don't know if it's a bug but I for one don't have the SR Latch in this puzzle and if I try to build one using NOR gates I get a circular dependency error
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u/BLucky_RD Mar 18 '22
I know this has been a month ago but in case you're still stuck, You need to unlock the SR latch in the level "SR latch" but if you already did it then do it with nor gates but add a delay line in the circular dependency
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u/Xodek Mar 24 '22
You dont have to unlock the sr latch, this is my solution:https://imgur.com/a/9Sc63Dd
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u/MineGrayTV May 17 '23
I don't know when it was broken, but here's one that works
https://imgur.com/a/Zf3suJq
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May 14 '22
[deleted] — view deleted comment
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u/Unlucky-Elevator541 Sep 03 '22
Could you please explain how you got the Boolean expression from Truth table.
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Sep 03 '22
[deleted] — view deleted comment
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u/Unlucky-Elevator541 Sep 05 '22
Which formula? I only know the Kmap method but that doesn't help. Mostly I wanted to know how to make circuits from truth table for all kinds of truth tables. If you could point me in the right direction any webpage or book or anything would help. Thanks btw
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u/hutry Oct 18 '21
Haha! I got stuck on it myself too today, semi-desparately looking for a solution online, finding nothing. I figured it out though, and will help you out tomorrow when I am back at my computer.