National Instruments 3.22E+04 用户手册

The following sections describe the advanced port setting options.

This field shows the transceiver mode in use, and applies only to PCI-485 
boards. For more information about transceiver modes, refer to Chapter 4, 

FIFO buffers are present on the 16550-compatible UARTs—one for the 
transmitter and one for the receiver. The Receive Buffer control sets the 
number of characters received in the FIFO before the PC is interrupted to 
read the data. The Transmit Buffer control sets the maximum number of 
bytes written to the FIFO in a block when the PC is interrupted to write the 
data. When you configure FIFO settings, consider the following points:

•

You can select larger FIFO buffer sizes to reduce the number of 
interrupts your PC receives and therefore minimize system overhead.

•

If transfer rates are high, you can lower the Receive Buffer value to 
prevent overrun errors due to interrupt latency.

•

If your data transfer sizes are small and your Receive Buffer value is 
above your data sizes, your system is less efficient. Therefore, set the 
Receive Buffer value below your data sizes.

To reset the fields to their default values at any time, click on the Restore 
Defaults button.