# Predetermined clock signal generation with sequential logic

#### 5O5mm

Joined May 15, 2021
15
Hi,

The signal has different frequencies each having different time durations and there is always a constant delay between them. Frequencies, durations are known, the timings (order of the frequencies) are also known and it goes like this depending on how many frequencies there are. Is it possible to achieve this with combinational logic? I already made it in a microcontroller pretty easily but not everything is code you know.

(And the signal in the bottom is another part I'd like to ask. After obtaining such a signal could we sum by AND'ing with another one having same timings but different frequencies?)

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#### BobTPH

Joined Jun 5, 2013
6,508
Assuming the timing is achievable, a microcontroller is by far the best solution.

Bob

#### 5O5mm

Joined May 15, 2021
15
Assuming the timing is achievable, a microcontroller is by far the best solution.

Bob
Thanks, I already did it with a uC but wondered if it is doable with logic ICs (It's not even a homework I asked in digital design section but they moved the thread

#### BobTPH

Joined Jun 5, 2013
6,508
With enough logic you can do anything a micro can do, so, yes.

Edit: Just re-read the title. No, you cannot do it with combinatorial logic. You need sequential logic.

Bob

#### Papabravo

Joined Feb 24, 2006
20,122
F
Thanks, I already did it with a uC but wondered if it is doable with logic ICs (It's not even a homework I asked in digital design section but they moved the thread
Maybe this section should be labeled "Homework Help & Nonsensical Hypotheticals with No Practical Applications". Would that make you happier?

#### 5O5mm

Joined May 15, 2021
15
F

Maybe this section should be labeled "Homework Help & Nonsensical Hypotheticals with No Practical Applications". Would that make you happier?
No I'm okay with that. I just didn't want to be seen as a lazy student who is asking hws in forums sorry if I'm misunderstood

#### BobTPH

Joined Jun 5, 2013
6,508
F

Maybe this section should be labeled "Homework Help & Nonsensical Hypotheticals with No Practical Applications". Would that make you happier?
That’s a bit harsh. I assume he meant sequential logic or didn’t understand the difference, which makes the question reasonable.

Bob

#### Papabravo

Joined Feb 24, 2006
20,122
That’s a bit harsh. I assume he meant sequential logic or didn’t understand the difference, which makes the question reasonable.

Bob
I was poking at the movement of the post to Homework Help, based on a presumed assumption of that nature. The implication seems to be that the question lacked some quality that would allow it to stay in its original position.

#### MrAl

Joined Jun 17, 2014
10,054
Hi,

The signal has different frequencies each having different time durations and there is always a constant delay between them. Frequencies, durations are known, the timings (order of the frequencies) are also known and it goes like this depending on how many frequencies there are. Is it possible to achieve this with combinational logic? I already made it in a microcontroller pretty easily but not everything is code you know.

(And the signal in the bottom is another part I'd like to ask. After obtaining such a signal could we sum by AND'ing with another one having same timings but different frequencies?)
View attachment 255309
Hi,

In the strictest sense of the phrase 'combinational logic' you can do anything that does not need to rely on the history of the inputs.

That's the bottom line, but since with real life we can combine combinational logic in such a way as to create memory and complex clocks, that means in real life we can do anything starting with only logic gates and inverters. For example, you can create a JK Master/Slave flip flop and that can be quite complex in itself.
Keep in mind real life gates also come with intrinsic signal delays and that may be needed for some circuits.

There is one exception i know of though, and that is we cant create a genuine random number generator, but with enough gates we can get really close such that the repetition period could be years.