clearing serial port

[mixo]

I have one tiny irritating problem :

Here is what I do:

   Clear Request To Send (~CRTS)
   Read from port
   sleep

My problem:

Should the device be turned off whilst readings are being taken,
I get the previous reading, which means I need to clear the
input from the device, before reading from the port. What
usually happens is that I get an additional reading without
any input, then reading returns to normal.

How do clear information that has been previously sent to the port?

Mixo