Digital Logic Toolkit

Digital Logic Toolkit — Logic gate symbols

Source
https://digitallogictoolkit.com/logic-gate-symbols/
Printed

OR — IEEE curved back vs IEC `≥1` — logic gate symbols

introthe threshold reading of OR

Answer

output column 0111

Why this example is worth doing

The IEC qualifier for OR is ≥1, which is not decoration: it says the output is true when at least one input is true, and it generalises. Change it to ≥2 and you have a majority-of-three voter; change it to =1 and you have XOR. The rectangular set is a small language for describing threshold functions, where the distinctive set is a fixed vocabulary of shapes. Explaining that makes the IEC symbols memorable rather than something to be tolerated.

Try your own input in the Logic gate symbols. Every gate in both symbol standards, side by side, on a printable one-page chart.

How the answer is reached

Truth table

Truth table — columns #, A, B, A + B
#ABA + B
0000
1011
2101
3111

Compare with

Open the Logic gate symbols

This input is entered in the tool itself — it is too rich for a link to carry.

Note:

Notation this page assumes

  • Symbols: · is AND, + is OR, ⊕ is XOR, a prime or an overline is NOT. The field also takes ∧ ∨ ¬ ~ ! & | and the words.
  • Operator precedence, tightest first: NOT, then AND (including juxtaposition), then XOR/XNOR, then NAND/NOR, then OR, then IMPLIES, then IFF.
  • Gate symbols follow whichever standard the header toggle is set to: ANSI/IEEE Std 91-1984 distinctive shapes, or IEC 60617-12 rectangles.

Sources

  • ANSI/IEEE Std 91-1984, Graphic Symbols for Logic Functions
  • IEC 60617-12, Graphical Symbols for Diagrams — Binary Logic Elements