Hi im using the serial port to poll a RFID reader on the rs232 port of the pda. The RDIF reader uses the CTS to indicate its ready status. I noticed in my code that i had not set CTSHandshaking to TRUE which explained the varied results i was getting. However, when i enabled this feature all i get is an exception when i try to transmit any data; my serial setup code is; If serial.PortOpen = False Then serial.CommPort = 1 serial.StopBits = 17 serial.dataBits = 8 serial.BitRate = 9600 serial.Parity="N" Serial.Timeout = 220 serial.PortOpen = True serial.EnableOnComm = False serial.XonXoffHandshaking = False serial.CTSHandshaking = True Sleep(500) End If then on a timer to poll for RFID tags i send a byte, wait for the RFID to work and then read back the data If serial.CTS = False Then serial.Output( "U" ) ' !!! EXCEPTION HERE !!! '' Sleep(100) '' wait for 8 bytes of data cnt=serial.InBufferCount timeout=120 Do While (cnt<8) AND (timeout>0) cnt=serial.InBufferCount timeout=timeout-1 Sleep(1) Loop '' process the 8 bytes etc .... End If If i dont set CTSHandshaking to true it all works - well without propper device timing. Any thoughts / help appreciated !