Boolean Logic Sequencer Error

[Xeys42]

I made a quick patch demonstrating the following anomaly. If you look at the attached images the first one shows the And operator working as it should, i.e. the sequencer doesn't run, however, when I select Nor and Xnor the sequencer runs. This shouldn't happen as A is on and B is off which defies the logic, and yes I have pressed the stop button before changing the modes. I'm wondering if this is a bug. Maybe it's something to do with the LFO However, changing the rate doesn't change anything.

and operator

and.png (1.13 MiB) Viewed 8736 times

nor operator

nor.png (1.1 MiB) Viewed 8736 times

xnor operator

xnor.png (1.09 MiB) Viewed 8736 times

[ColinP]

This is the expected behaviour.

One of the inputs is disconnected therefore always zero, let's say it is the B input that's disconnected
so B = 0

Looking at the truth table for NOR

A B Q
0 0 1
0 1 0
1 0 0
1 1 0

Now when A (the LFO) is 0 the output is 1.
When A is 1 the output is 0.

With XNOR...

A B Q
0 0 1
0 1 0
1 0 0
1 1 1

Same result.

So in both circumstances the clock is just being inverted and the sequencer advances (albeit a half cycle out of phase).

[ColinP]

Also if your intention is for the LFO to control the tempo of the sequencer you need to feed its output to the sequencer's EXT CLK socket and engage the EXT button as shown below.

lfoAsClock.png (266 KiB) Viewed 8705 times

You could then add an AND gate into this path to enable or disable the LFO's external clock signal (which is what I'm guessing you were experimenting with).

In your screenshots the LFO is just starting the sequencer and the sequencer is running on its own internal clock. So the only impact the LFO RATE knob will have is how quickly the sequencer starts.

[Xeys42]

Thanks for replies ColinP. No that wasn't my intention although I will try that.

So in both circumstances the clock is just being inverted and the sequencer advances (albeit a half cycle out of phase).

So from what I understand the LFO inverts the signal? can you expand on this a little more if you don't mind.
Edit: How did I miss that, penny drop moment. Of course the LFO is cycling on and off, D'oh!

[ColinP]

Hi, I hope my posts helped a bit.

The inversion is caused by the NOR or XNOR gates.

The little circle on the output of a logic gate symbol indicates that logical inversion (NOT) is applied to the output so that's one way to understand that a NAND gate is an AND gate followed by an inverter, a NOR gate is an OR gate followed by an inverter etc.

Unfortunately XNOR has come to be used for what I think ought to be called an NXOR gate so this adds a bit of confusion.

Ah, so I'm guessing you were just using the Mini LFO as a source of a test pulse. You might find this module useful...
https://store.cherryaudio.com/modules/buttons-21

Roland (P. Moon) kindly published this for free years ago and I think virtually everbody uses it in test rigs.

[Aarnville]

All of that stuff is why I made the Transporter module. I was spending too long fiddling with logic gates just to start and stop a couple of sequencers.
I originally made it just for myself but it turned out to be one of my bestsellers!

[Xeys42]

Thanks ColinP, yes they did help. I will try the buttons module, I downloaded it recently.

The inversion is caused by the NOR or XNOR gates.

Now I'm more confused. If this is so it sounds to me like they are doing what they shouldn't be. I give up, lol. I think you had the right idea Aarnville.

[utdgrant]

The inversion is caused by the NOR or XNOR gates.

Now I'm more confused. If this is so it sounds to me like they are doing what they shouldn't be. I give up, lol.

No, they're working fine. It's the fact that there is no signal connected to the right-hand input of the logic gates which explains Colin's thinking. This is equivalent to the 'B' input in any truth tables always being '0' or 'Low'.

The OR and XOR gates function as buffers of the left-hand (or 'A') input.
The NOR and XNOR gates function as invertors of the left-hand (or 'A') input.

OR-XOR-NOR-XNOR.jpg (132.91 KiB) Viewed 8482 times

[SpaceDog]

Thanks ColinP, yes they did help. I will try the buttons module, I downloaded it recently.

The inversion is caused by the NOR or XNOR gates.

Now I'm more confused. If this is so it sounds to me like they are doing what they shouldn't be. I give up, lol. I think you had the right idea Aarnville.

From a simple point of view, as I always look for the simple solution, if you're working with VM in standalone mode, just buy Aarnville's Transporter, it's only $2.50. Yes, you can create what it's doing, but for that price just buy it and get on with the music. You can always do the clever stuff later

If you're working within a DAW, use an AND gate with a clock signal (I derive mine from the CA SYNC Divider module) and the Play Gate as the inputs - that will give you a synchronised clock signal when the DAW is playing/recording. If you need syncronised gates as well (e.g. for envelopes), use a trigger to gate module on that derived clock signal.

[Xeys42]

Still doesn't add up. The way I see it is this:

Looking at the 3 pictures on my first post above:

'And' works as expected as input 1 is on and input 2 is off.
'Nor' and 'Xnor' don't work as expected as 1 is on, 2 is off and according to truth tables in this state the output should be off.

I went on the test the Boolean module by having nothing plugged into the inputs and only the output plugged into the sequencer. Obviously this means both inputs are off. All the 6 different boolean modes worked as expected in this case.
This backs up my original theory that the LFO pulse wave signal must be inverting the output, not the module itself as suggested in one of the replies above.

Thanks Spacedog. I must point out I'm not actually trying to achieve anything specific at this stage I'm basically experimenting with different modules to gain a deeper knowledge of voltage modular. Perhaps some interesting, unique ideas will emerge as a result.