National Instruments PCI-8430, Manual

Page: 96 / 237

FIFO Buffers
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.
The built-in ports on PXI RT controllers and the PCI, PXI, and PCMCIA
plug-in serial boards have configurable FIFO settings. Use the
Advanced
tab in MAX to configure your FIFO settings. 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 thereby 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. For
maximum efficiency, set your Receive Buffer value such that your
data transfer size is a multiple of that value.