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hneemann / Digital

A digital logic designer and circuit simulator.
GNU General Public License v3.0
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Custom 744511 causes oscillation #1261

Open Knochi opened 9 months ago

Knochi commented 9 months ago

Hi,

Digital v0.30

I'm developing a single button stopwatch with latch function to save the last round.

image

First i used the standard 7448 7-Segment decoder plus discrete latches (74174) but then i found the 744511 which is a 7-segment decoder plus latch.

Sometimes, when I repeat the test several times, I get an Error:

image

First of all, is this something I should care about before implementing in real world electronics?

If yes.. how can i debug this? The circuit for the 744511 was discussed here on reddit. I used the corrected "ideal" schematic, should i use the TI one with added gates?

Thanks in advance

Added the files here, if someone wants to dig in deeper. SBDS_SingleButtonDigitalStopwatch.zip

mengstr commented 9 months ago

I guess the culprit here is the NOR-based S/R latches in your homemade D-latch that is a part of the '4511. They tend to be a bit evil and oscillate in simulations - and if the enable-pulse to them is too short they always go into oscillation.

There's a new pre-release of Digital that has a feature that makes oscillations die down by themselves. See discussion #1230 for a link to the download.