Eaton ELC-PB - Page 6

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ELC Concepts
This chapter introduces basic and advanced concepts of ladder logic, which is the
most used programming language with the ELC. Users familiar with the ELC
concepts can move to the next chapter for further programming concepts. Users
not familiar with the operating principles of the ELC, should read this chapter to get
a full understanding of these concepts.
This Chapter Contains
1.1 ELC Scan Method .................................................................................................................1-2
1.2 Current Flow..........................................................................................................................1-3
1.3 NO Contact, NC Contact ......................................................................................................1-3
1.4 ELC Registers and Relays ...................................................................................................1-4
1.5 Ladder Logic Symbols .........................................................................................................1-5
1.5.1 Creating a ELC Ladder Program...............................................................................1-6
1.5.2 LD / LDI (Load NO contact / Load NC contact) .........................................................1-7
1.5.3 LDP / LDF (Load Rising edge trigger/ Load Falling edge trigger) .............................1-7
1.5.4 AND / ANI (Connect NO contact in series / Connect NC contact in series).............. 1-7
1.5.5 ANDP / ANDF (Connect Rising edge in series/ Connect Falling edge in series)......1-7
1.5.6 OR / ORI (Connect NO contact in parallel / Connect NC contact in parallel)............1-8
1.5.7 ORP / ORF (Connect Rising edge in parallel/ Connect Falling edge in parallel) ......1-8
1.5.8 ANB (Connect block in series) ..................................................................................1-8
1.5.9 ORB (Connect block in parallel) ................................................................................1-8
1.5.10 MPS / MRD / MPP (Branch instructions)................................................................... 1-9
1.5.11 STL (Step Ladder Programming).............................................................................1-10
1.5.12 RET (Return) ...........................................................................................................1-10
1.6 Conversion between Ladder Diagram and Instruction List Mode................................. 1-11
1.7 Correcting Ladder Diagram ...............................................................................................1-14
1.8 Basic Program Design Examples .....................................................................................1-17