Serial read operation not getting timed out despite setting serialport.readtimeout property?

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C#

serial-port

I am developing an HMI for displaying the data acquired from 8 (Data Acquisition DAQ) cards each having 8 channels through serial port (RS-232).

I want to implement a time-out operation in which the HMI should dispay a message if a particular DAQ card wasn't able to serially send its acquired data within a specific time interval (let's say 20 seconds), and then continue to acquire data from the remaining cards.

For this I am setting the serialPort.ReadTimeout = 20000 but the operation isn't getting properly timed out as expected.

I am using the BackgroundWorker class to serially send and acquire data of 4000 samples from the cards and it is working fine except for the time-out function. Can anyone point out the issue?

What I have tried:

//code snippet
    serialP.DataBits = 8;
    serialP.StopBits = StopBits.One;
    //serialP.Handshake = Handshake.RequestToSend;
    serialP.Parity = Parity.None;
    
    serialP.DataReceived += serialP_DataReceived;

    serialP.WriteTimeout = 20000; 
    serialP.ReadTimeout = 20000;
    
    serialP.Open();            
   
    serialRtx.DoWork += serialRtx_DoWork;            

    if (!serialRtx.IsBusy)
        serialRtx.RunWorkerAsync();

    serialRtx.RunWorkerCompleted += serialRtx_RunWorkerCompleted;
    
}

    private void serialRtx_DoWork(object sender, DoWorkEventArgs e)
    {
     //Send token packets to DAQ cards sequentially
    }

    private void serialP_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        while (serialP.BytesToRead > 0)
        {                
            dataBytet1 = serialP.ReadByte();                
            dataByte2 = serialP.ReadByte();                               
                           
            try
            {               
                logData[sample_No, chNo - 1] = ((dataBytet1 * 256) + dataByte2 );                     

                chNo++;

                if (chNo > 8)
                {
                    sample_No++;
                    chNo = 1;
                }

                if (sample_No > 3999)//total 4000 samples of 8 channels
                {
                    cardNo++;
                    sample_No = 0;
                }                
            }
            catch (IndexOutOfRangeException)
            { }                
        }
    }