i hope anyone can help me

i am trying to send a string of characters (ascii codes 0 to 255) over the serial port using the SerialPort control in C# (vs 2005 pro)

the characters arrive nice and sweet ... up to 7F, the characters with ascii code 80 and higher (hex) are sent as 3F all the time (as soon as the 8th bit is used 3F will be sent)

does know anyone what could cause this problem, and maybe how it can be solved or done otherwise ?

i am using the code below :

string strMsg = "";
for (int intI = 0; intI <256; intI++)
{
  strMsg += Convert.ToChar(intI);
}
comKAR.Write(strMsg);
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