Ladder compare, move, math, edge and latch blocks
The blocks that work on numbers and edges: comparisons that act like contacts, move and math that write values, edge detection, and set and reset bistables.
SymbolIEC 61131-3What it is
Greater than or equal (GE)Compares IN1 and IN2 and passes power when IN1 ≥ IN2 (greater than or equal).
SR set-dominant bistableA latch where set wins: Q1 goes true on S1 and false on R, and if both are true, Q1 stays true.
RS reset-dominant bistableA latch where reset wins: Q1 goes true on S and false on R1, and if both are true, Q1 is false.
Compare, move and logic blocks
A comparison block such as EQ or GT passes power when its comparison is true, so it is used like a contact. Move and math blocks run when the rung is true and write their result to a tag.
Frequently asked questions
Which compare, move and logic blocks appear on a ladder diagram?
This legend covers equal (EQ), not equal (NE), greater than (GT), greater than or equal (GE), less than (LT), less than or equal (LE), MOVE (MOV), ADD, R_TRIG rising edge, F_TRIG falling edge, SR set-dominant bistable, RS reset-dominant bistable. Project legends may add more.
Can I download these symbols?
Yes. Each symbol page has free SVG files, and the hub has printable PDF charts.
Every interlock in your PLC logic, tested and signed.Deskely holds the cause and effect and function test records for every system, checked as they are signed, so the logic is proved before start-up.
- In production since 2014
- Thousands of daily users
- On MODEC FPSO projects since 2016