Hi everyone,
While making a schematic entry, when one invokes the symbol of a TTL device having multiple copies (2, 4,or 6) of one functional gate type, it also contains one part with just Vcc and Gnd terminal. The symbol for this part is comparitively bigger than the symbol of the actual functional gate.
Example: Consider the logic symbol for “74LS08”, a Quad 2-input AND gate device.
The library offers the four 2-input AD gates plus one symbol just including Vcc & Gnd (pin 14 & 7 of the device package) of the device. This size of this symbol drawing much bigger than that of the actual AND gates.
If the circuit contains many TTL gates (which I suppose is quite normal in a typical design) and one has to include the “Vcc & Gnd” symbol part of all of those on the schematic this is very space consuming und complex.
Questions 1: Is there a way to resize (reduce the size) or any other method to overcome this space issue due to “Vcc & Gnd” symbol part of TTL devices?
This probably should be a new topic, but if there is a way to scale symbols (on the schematic, not in the library) that I’m not aware of I’d like to know. Some symbols are too large and some too small. I don’t need continuously variable scaling, even powers of two would be acceptable.
An example is the symbol for each of the inverters in the 7404. It’s just two pins but so big.
No, there is no scaling. Just copy the library to your own space, change symbol names to xxxx_small and reduce their size. Optionally also change the library name to remind you what is going on.
Hi Piotr
Thanks for your suggestion to copy, modify and using as personal symbol. I will definitely try that.
Meanwhile, as a quick space saving alternative on the schematic sheet, I found that one can also change the symbol properties and choose the so called De Morgan representation of the symbol. In case of power symbol for TTL devices the De-Morgan representation is quite slim and with reducing the text size from 50,000 mils to 35,000 mils it is quite ok.
However, I found that choosing De Morgan representation is not possible for all power symbols. The De Morgan representation box is greyed out and cannot be selected.
In my case I tried 74LS32 and 74LS04. De Morgan representation for 74LS32 is possible, but not for the 74LS04 device.
For ease of understanding, I have attached a word file with screen shots of two symbol property editing fields and below that the symbols in normal (KiCad lib version) and De Morgan representation.
I believe, that for the 74LS04 device where the De Morgan representation field is greyed out, there must be some hidden flag somewhere which needs to be set correctly.
I would be greatful to you If you could kindly help me with the info as to where do I have to make correct settings, please.
Thanks for your help in advance.
Best regards191210 KiCad symbols De-Morgan representation.docx (85.9 KB)
When someone designs a symbol he can add the another symbol representation called De Morgan. He must define the graphic for it. If he didn’t added such picture then you can’t select that unexisting picture.
First time I sow it used this way that for example NAND symbol can have 3 pins or 5 pins (NAND + power supply pins). So when using 7400 you used 3 normal symbols and one De Morgan to connect supply for the whole IC. I suppose it was intended use of De Morgan, but not sure. Now KiCad library designers decided that they will add special 5-th symbol only for power supply. I don’t know if it was made for all digital libraries. I practically don’t use digital ICs (except few 1G ICs).
That way De Morgan is not needed for those ICs. May be someone decided to add smaller power symbol but forgot to add it for all ICs.
As previously you can copy IC symbol definition and modify power part or add for it De Morgan.