I have been working on new symbols for the 7400 logic library (74xx.lib). One major goal is to remove hidden VCC/GND pins, which are now considered “old hat”. Additionally, the current symbols lack consistency and most are not conformant to latest library conventions (KLC 2.0.4)
Therefore I have extracted data from the current lib, and regenerated the symbols using a script. Some of the existing symbols already have visible power pins, so I have not included those in the new library, which for now I will refer to as “74xx_new.lib”
I have created “contact sheets” for the existing and new libraries. Some notes
- this is work in progress, so there are several symbols still to be tidied up.
- if all units in the component are interchangeable then only the first unit is shown
- the KiCad output to PDF does not show hidden pins
- not shown are De Morgan equivalents, I have not implemented these in 74xx_new
Hopefully this shows the general direction - at this stage it is a proposal and nothing is set in stone. It’s important to note that the new lib is not backward compatible with the existing lib. There are too many changes so I felt a “clean sweep” is the only practical way forward.
There is one major restriction placed by KiCad : all units must have the name and reference in the same position. In some cases, this causes the text to overlap the symbol, which is not ideal.
Existing 74xx.lib (github latest)
7400_old.pdf (390.9 KB)