1 Basic Principles of PLC Ladder Diagram The structure of a ladder diagram: DVP-PLC Application Manual 1-6 Device Functions Index register E and F index registers are 16-bit data registers as other data registers. They can be read and written and can be used in word devices, bit devices or as a constant for index indication. Device indication: E0 ~ E7, F0 ~ F7 are indicated as E and F and numbered in decimal form.
Structure Explanation Instruction Devices Used Normally open, contact A LD X, Y, M, S, T, C Normally closed, contact B LDI X, Y, M, S, T, C Normally open in series connection AND X, Y, M, S, T, C Normally closed in series connection ANI X, Y, M, S, T, C Normally open in parallel connection OR X, Y, M, S, T, C Normally closed in parallel connection ORI X, Y, M, S, T, C Rising-edge trigger switch LDP X, Y, M, S, T, C Falling-edge trigger switch LDF X, Y, M, S, T, C Rising-edge trigger in series connection ANDP X, Y, M, S, T, C Falling-edge trigger in series connection ANDF X, Y, M, S, T, C Rising-edge trigger in parallel connection ORP X, Y, M, S, T, C Falling-edge trigger in parallel connection ORF X, Y, M, S, T, C Block in series connection ANB - Block in parallel connection ORB -