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Chapter 5: Basics of PLC Programming - Coggle Diagram
Chapter 5: Basics of PLC Programming
5.2: Program Scan
There are typical steps involved when wanting to know how to outline the sequence of events involved in a PLC scan cycle
Summary of the steps: Closed input makes input bit 1, which triggers the processor to set the output bit, energizing the output (light) on the next scan, repeating in RUN mode.
5.3: PLC Programming Languages
There are five standard PLC languages as defined by the International Standard for Programmable Controllers
These five include Ladder Diagram (LD), Function Block Diagram (FBD), Structured Text (ST), Instruction List (IL), and Sequential Function Chart (SFC)
5.4: Relay-Type Instructions
Three significant Ladder Logic instructions include NO (Normally Open) contact, NC (Normally Closed) contact, and coil.
NO checks 1(ON), NC checks 0(ON)- if true, rung executes for that specific contact. Coil energizes if conditions are met.
5.5: Instruction Addressing
To set up a relay instruction, assign each address to match PLC inputs with input devices and PLC outputs with output devices.
An assigned address for an input device could look like this for example: I: 3/4. An assigned address for an output device could look like this for example: O: 5/6
5.6: Branch Instructions
Branch instructions are used to create parallel paths of input condition instructions.
This allows more than one
combination of input conditions and also allows for logic continuity in a rung
5.7: Internal Relay Instructions
Internal outputs differ from a discrete outputs
An internal output is for logic processing, while a discrete output controls a physical device.
5.8: Programming Examine If Closed and Examine If Open Instructions
Examine if Open and Examine if Closed Instructions are two completely different instructions that can be used in different scenarios in PLC Programming.
Examine if Open (XIO) checks if a bit is OFF (0); if true, the rung continues. Examine if Closed (XIC) checks if a bit is ON (1); if true, the rung continues.
5.9: Entering the Ladder Diagram
Regardless of what device you are using, there are specific windows that you will need to use when working with RSLogix 500 software.
These include the Main Window, the specific Processor Type, I/O Configuration, and Data Files.
5.1: Processor Memory Organization
the memory map for a typical PLC processor consists of two types of files. One type is known as Data Files and the other is known as Program Files
Program files store the logic of the PLC while data files typically contain values, variables, and status information used during PLC execution
5.10: Modes of Operation
There are four different modes of operation that we must consider when referring to PLC Programming
These include Program Mode, Run Mode, Test Mode, and Remote Mode