Is there a mistake in this microcontroller schematic?
Figure 1. The red circles (e.g., number 1) show connections between 'wires'. The green circle (number 2) shows wires crossing without connection.







simulate this circuit &ndash; Schematic created using CircuitLab

Other schematics including the built-in CircuitLab schematic editor use a semi-circular loop at non-connected crossing points.

Figure 2. The CircuitLab standard.




  @Neil_UK adds, "you might add, that's why we hate the 4 way crossing as in the red (1), because dots don't always survive copying/transcription/ink blots." 




Figure 3. Wikipedia's Circuit diagram article gives further details on this matter.



Figure 4. Meanwhile, over at Dummies.com we find another set ...

The nice thing about standards is that you have so many to choose from. (Andrew S. Tanembaum).