# Detect the first rising edge of 3 input signals

I have 3 input signals which are pulse waveforms The output is switch to high once once all 3 first rising edges of 3 inputs are detected. Is there a digital circuit from logic gates, flip flop that can do that? I am thinking about flip flop but the problem is that it detects with every rising edge not just the first rising edge.

• And when does out go low? – Tyler May 10 '19 at 0:31
• You need a combination of Flip-Flops and logic gates. – Mattman944 May 10 '19 at 0:34
• Are you trying to detect if y and z go high before the second rising edge on x? Or, if they went high after the second rising edge, would that also result in the output going high? – Annie May 10 '19 at 0:42
• @Tyler it will remain high from that time – anhnha May 10 '19 at 1:54
• @Annie: no, the order doesn't matter, only detect the first rising edges of 3 inputs. After the first rising edges of 3 inputs are detected, the output goes high and remains at that value – anhnha May 10 '19 at 2:05

• I accept you arguments, but the drawing is way to inaccurate to say X is definitely down :). – Paebbels May 14 '19 at 23:22