Function SetMfxRegValue6021(thisPort As Integer, thisRegister As Integer, thisNewValue As Integer) : Boolean
 
begin
 
  // (c) DiegoGarcia and Family, Germany
  // 19.04.2007
  // RealBasic 2007-02 subroutine (Mac, Lin & Win)
  // Purpose: write "thisNewValue" into "thisRegister"-RegV of any FX-/MFX-decoder
  // through the serial port indicated by "thisPort", where a mae6021/mae6051 is connected
  // Assuming: "Serial1 As Serial" defined in calling window or global "App"
  
  const ckue = "ü"  // for German message text
  const ckea = "é"   // for French message text
  const ckag = "à"
  
  const Vturn = 15  //mae6021 / P50 syntax = change direction; apply only on non-moving locos!
  const Vstop = 0    // mae6021 / P50 syntax = speed 0, no loco moving
  const DefaultMFXLocoAdr = 80   // address 80 is used to access any FX/MFX decoder, no matter what address it has
  dim oldCTS As Boolean   // to store existing status
  dim myGoOn As Boolean
  
  myGoOn = TRUE
  
  if (thisPort >= 0) and (thisPort < System.SerialPortCount) then  // check bounds
    
    Serial1.SerialPort = System.SerialPort(thisPort)
    
    Serial1.Baud = GetActualBaud   // this MUST be done before Serial1.Open !!!!!!!
    Serial1.Parity = GetActualParity
    Serial1.Bits = GetActualDataBits
    Serial1.Stop = GetActualStoppBits
    Serial1.CTS = GetActualCTSflowcontrol
    
    // try to open the serial port
    if not Serial1.Open then
      // we failed to open the port, quit this subroutine
      MsgBox "Could not open " + System.SerialPort( thisPort ).Name
      // perhaps another application is using this port or access rights are missing
      myGoOn = FALSE
    else
      
      // 0) instruction to the user: reset the mae6021 manually, sorry, no command for this task
      ShowProgrammingMode(TRUE)
      DisplayInfoText(0)
      select case App.gLanguage
      case 1
        myGoOn = App.MessageWithCancel("Pressez simultan" + ckea + "ment les touches GO et STOP jusqu'" + ckag + " ce que le num" + ckea + "ro '99' clignote sur l'" + ckea + "cran.")
      case 2
        myGoOn = App.MessageWithCancel("Bitte die Mrkl6021 zur" + ckue + "cksetzen durch gleichzeitiges Dr" + ckue + "cken der GO und STOP Tasten, bis '99' in der Anzeige aufblinkt.")
      else
        myGoOn = App.MessageWithCancel("Please reset the mrkl6021 by pressing GO and STOP simultaneously for several seconds until '99' blinks in the display.")
      end select
      
      if myGoOn then
        
        // 1) sending STOP command
        DisplayInfoText(1)
        WriteByte(97)                                           // Nothalt / STOP
        Wait150miliseconds   // sending twice, to compensate a wrong byte order of preceeding commands
        WriteByte(97)
        WaitSeconds(1)   
        
        // 2) disable CTS, because the 6050/6051 interface should tell CTS=FALSE after STOP command
        oldCTS = Serial1.CTS
        Serial1.CTS = FALSE                                 // to enable data sending in any case
        
        // 3) send message to turn any FX/MFX decoder into programming mode
        DisplayInfoText(2)
        WriteByte( Vstop )                                    // send speed = 0 to stop motor
        Wait150miliseconds
        WriteByte( DefaultMFXLocoAdr )               // addr = 80
        Wait150miliseconds
        
        WriteByte( Vturn )                                    // send speed = 15 to turn direction
        Wait150miliseconds
        WriteByte( DefaultMFXLocoAdr )               // addr = 80
        Wait150miliseconds
        
        DisplayInfoText(3)
        WriteByte(96)                                            // Freigabe / GO
        WaitSeconds(1)
        // now the mae6021 will fire always "turning" command to loco addr 80
        // and the head-lights of the MFX-/FX-loco should blink continously on both sides
        
        // 4) re-eanable CTS
        Serial1.CTS = oldCTS
        
        // 5) write RegV-entry address
        // sequence doesn't matter, you can turn off DefaultMFXLocoAdr's turning command before adressing thisRegister
        DisplayInfoText(4)
        WriteByte( Vstop )                                    // send speed = 0 to stop mae6021 firing "turning" command
        Wait150miliseconds
        WriteByte( DefaultMFXLocoAdr )              // addr = 80
        Wait150miliseconds
        
        WriteByte( Vstop )                                    // send speed = 0 to stop motor, preparing RegV to receive data
        Wait150miliseconds
        WriteByte( thisRegister )                          // addr = RegV address range 1..79
        Wait150miliseconds
        
        WriteByte( Vturn )                                    // send speed = 15 to indicate RegV to receive data
        Wait150miliseconds
        WriteByte( thisRegister )                          // addr = RegV address range 1..79
        WaitSeconds(2)                                        // wait a little bit longer
        
        // now the head-lights of the loco should blink in a faster scheme
        
        // 6) write new value to this RegV
        DisplayInfoText(5)
        WriteByte( Vstop )                                    // send speed = 0 to stop mae6021 firing "turning" command
        Wait150miliseconds
        WriteByte( thisRegister )                          // addr = RegV address range 1..79
        Wait150miliseconds
        
        WriteByte( Vturn )                                    // send speed = 15 to indicate the data
        Wait150miliseconds
        WriteByte( thisNewValue )                        // addr = value range 1..80, depending on RegV's definition of the decoder
        Wait150miliseconds
        
        // now the head-lights of the loco should blink in the slower scheme
        
        WriteByte( Vstop )                                    // send speed = 0 to stop mae6021 firing "turning" command
        Wait150miliseconds
        WriteByte( thisNewValue )                        // addr = RegV address range 1..79
        WaitSeconds(2)                                        // wait a little bit longer
        
        // 7) terminate decoder programming mode
        DisplayInfoText(6)
        WriteByte(97)                                           // Nothalt / STOP
        
        // now the loco's head-lights should be off
        
        WaitSeconds(1)
        Serial1.CTS = FALSE                                 // to enable data sending in any case
        WriteByte(96)                                            // Freigabe / GO
        Wait150miliseconds
        Serial1.CTS = oldCTS
        
        // done, now the mae6021 should be again in normal operation mode
        // and the loco's decoder should have the new value "thisNewValue" entered in its RegV "thisRegister"
        // sorry to say that there is now way to read RegVs using a mae6021/mae6051 combination.
        
      end
      ShowProgrammingMode(FALSE)
      
    end
  else
    myGoOn = FALSE
  end
  
  Return myGoOn
 
end function