How to turn of 16Bit FIFO of Serial Ports

[nobo]

Hi guys

there are several Threads on this topic all of them with no answer so im taking a further try.
Ive got a display with Rs232 providing Hardware Handshake RTS / CTS which is enabled and working.

So far so good now the tricky part. The Serial Port on the PC has got a FIFO of 16 Byte but the input Buffer of the display is only able to read further 4 Bytes after RTS is set to -10V indicating that no more bytes can be received. Now as the Display sets RTS to -10V the data stored in FIFO is still sent to the display causing unwanted behaviour if more than 4 bytes are sent.

The Question therefore is. Is there a way reduce the size of the FIFO used by the USART like it can be done in Device Manager (Win XP) or to completely turn the FIFO off.

Settings made in Device Manager do have effect but as they cannot be distributed a C++ solution would be prefered

Any help will be appreciated.

Regards nobo