A family of programming languages for programmable logic controllers (PLCs). Of the three graphical and two textual languages, ladder logic (see example below) was the first language and widely used.

Ladder logic uses switch or relay contacts to implement Boolean expressions. In years past, ladder logic was made possible with discrete relays and was sometimes termed “relay logic.” Today most ...

The PLCopen Motion Control Specification harmonizes the access of motion-control functionality across platforms, explains Eelco van der Wal, managing director of PLCopen (www.plcopen.org), Zaltbommel, ...