Quatech RS-232 - Manual (Page 27)

7. Open the Properties dialog for a COM port, then click the Port
Properties tab to view the settings for that port.
8. Click the "Port Settings" tab and then click the "Advanced"
button. The ESC(LP)-100 driver will display a custom
Advanced Port Settings control, which allows the ports UART
compatibility mode and FIFO threshold levels to be configured.
The threshold values of full-scale for the transmit buffer and
¾ -scale for the receive buffer are optimal for most applications.
Note that the FIFO option for each of the ESC(LP)-100's eight
ports is configured independently.
ESC(LP)-100 User's Manual 21