B&B Electronics 3PCIU4 - Manual (Page 47)

Setting Driver Options
Manual Documentation Number 3PCIoUx-1008 Chapter 4 41
The Advanced Port Settings dialog will appear. This screen allows
you to set the Receive and Transmit FIFO buffer thresholds, RTS
Control parameters, Hardware handshaking hysteresis level and the
COM port name.
Figure 31. The Advanced Settings for COM# dialog
Setting the FIFO Buffers
MIport cards use UARTs that contain 64-byte transmit and receive FIFO
(first in, first out) buffer registers. The transmit buffer holds the data to be
sent; the receive buffer holds the data received.
The Transmit buffer: Low parameter in the Advanced Port Settings dialog
allows you to set the minimum value at which the UART will request more
data from the computer. As the MIport card is transmitting data, the number
of bytes left in the transmit buffer will decrease. When the buffer reaches the
value set, the UART will request more data from program memory. This is
intended to optimize the throughput of the data. Typically this parameter is
set at zero and usually does not have to be changed.
The Receive buffer: Low parameter in the Advance Port Settings dialog
allows you to set the value at which the UART will request that the computer
read the data that has been received. As the MIport card is receiving data the
contents of the receive buffer increases, when it reaches the value set, the