Shift Register behaves very strange

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LogicFreak
Posts: 5
Joined: Wed Feb 17, 2021 2:21 pm

Shift Register behaves very strange

Post by LogicFreak »

Hello,
looking two hours already but cannot find the bug.
In attached project, 8 D-flipflops are cascaded to found a simple 8-bit shift register.
If switched on and one hits the data input button, one would expect a marching one, illuminating the leds left to right, one at a time.
This worky pretty well for the first 5 ones; at next clock, #6 ... #8 are switched on alltogether which obviously is wrong.
Any hint welcome!
Thanks, LogicFreak
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admin
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Re: Shift Register behaves very strange

Post by admin »

On your Q6 the lower input is incorrectly connected. The wire pans out for too much so both the Q7 and Q8 are disconnected.
There is a simple trick to find such problems: just play with Edit/Select... menus to see where are your wires and floating elements and what not.
LogicFreak
Posts: 5
Joined: Wed Feb 17, 2021 2:21 pm

Re: Shift Register behaves very strange

Post by LogicFreak »

Hmmmm ...
Looking for hours ... such simple.
Thanks for sharing your tricks. I'm learning every day ...
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