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Chapter 4 PCMCIA Serial Hardware Installation, Verification, and Configuration
© National Instruments Corporation 4-21 Serial Hardware and Software for Windows
FIFO Enabled
You can use the FIFO Enabled control to enable or disable the FIFO
buffers on the serial port. FIFO buffers are present on the
16550-compatible UARTs—one for the transmitter and one for the
receiver.
FIFO Buffers
The FIFO buffer control is available by clicking on the Advanced button
on the Port Settings tab. FIFObuffers are present on the 16550-compatible
UARTs—one for the transmitterand onefor the receiver.The receive FIFO
trigger denotes thenumber of characters received in the FIFObefore the PC
is interrupted to read the data. The transmit FIFO trigger denotes the
maximum number of bytes written to the FIFO in a block when the PC is
interrupted to write the data. Consider the following points when selecting
FIFO settings:
• You can select larger FIFO settings to reduce the number of interrupts
and therefore minimize system overhead.
• If transfer rates are high, you canlower receive FIFO settings to reduce
the number of interrupts and therefore prevent overrun errors due to
interrupt latency.
• If data transfer sizes are small, selecting receive FIFO settings just
above data sizes can reduce efficiency, so select lower settings.
Resources
ClickontheResources button to display the resource configuration dialog
box for the port. For more information on resource configuration, refer to
the next section, Resource Settings.