Implement the rising edge in C ＃, and simulate the PLC environment to verify the difference between if statement using the rising edge and not using the rising edge

PLC It can be thought that running in while The program in the loop （Ob100 With the exception of ）, every last OB Each block is a separate thread . Understand this , It can be better C# Upper computer programming and PLC Of SCL（ST） Programming .

stay SCL in , If If The condition of the statement uses a long signal ,If The statement will be executed repeatedly , Some exchange values , Transfer value , The operation of updating the value cannot be completed , Now If The condition of the statement must use transient signals ,If The condition of using rising edge is a good choice .

Rising edge ：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FPTest
{
    
    public class R_TRIG
    {
    

        ///
        ///  This attribute stores the last bool state ,get;private set; This is equivalent to PLC Of  Output Interface 
        ///

        public bool Last {
     get; private set; }

        ///
        ///  This attribute is filled with the detected bool The amount ,set; amount to PLC Of Input Interface 
        ///

        public bool CLK

        {
    
            set

            {
    
                Q = value && !Last;// We know that the rising edge is from 0 change 1 For a moment , Therefore, when this scan is true and the last one is false, a rising edge is generated 
                Last = value;// Refresh the reference bit every scanning cycle 
            }
        }

        ///
        ///  This is the state of detection , External access to this variable will know whether the rising edge has been generated 
        ///  amount to PLC Of  Output Interface 
        public bool Q {
     get; private set; }

    }

}

Falling edge

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FPTest
{
    
    public class F_TRIG
    {
    

        public bool Last {
     get; private set; }

        public bool CLK

        {
    
            set
            {
    
                Q = !value && Last;//1 change 0  Last time is true, this time is false 
                Last = value;
            }
        }

        public bool Q {
     get; private set; }

    }

}

The main program

namespace FPTest
{
    
    public partial class FrmMain : Form
    {
    
        public FrmMain()
        {
    
            InitializeComponent();
            rTrig = new R_TRIG();
            fTrig = new F_TRIG();
            this.label1.Text = a.ToString();
            this.label2.Text = b.ToString();
        }
        private R_TRIG rTrig;
        private F_TRIG fTrig;
        private int a = 0;
        private int b = 0;

        CancellationTokenSource cts = new CancellationTokenSource();

        private void btnUp_Click(object sender, EventArgs e)
        {
    
            
            Task.Run(async () =>
            {
    
                while (!cts.IsCancellationRequested)
                {
    
                    await Task.Delay(200);
                    rTrig.CLK = true;
                    if (rTrig.Q)
                    {
    
                        a = b;
                        b = int.Parse(this.textBox1.Text.Trim()) ;
                    }
                    this.label1.Invoke(new Action(() => {
     this.label1.Text = a.ToString(); }));
                    this.label2.Invoke(new Action(() => {
     this.label2.Text = b.ToString(); }));
                }
            }, cts.Token);
        }

        private void NoRTrig_Click(object sender, EventArgs e)
        {
    
            Task.Run(async () =>
            {
    
                while (!cts.IsCancellationRequested)
                {
    
                    await Task.Delay(200);
                    if (true)
                    {
    
                        a = b;
                        b = int.Parse(this.textBox1.Text.Trim());
                    }

                    this.label1.Invoke(new Action(() => {
     this.label1.Text = a.ToString(); }));
                    this.label2.Invoke(new Action(() => {
     this.label2.Text = b.ToString(); }));
                }
            }, cts.Token);
        }
    }
}

The initial state

Use rising edge ,If It was executed once in

Do not use rising edge ,a,b Unable to pass value