EF_PIO - UG1586

Name

pio

Default

1

Minimum

0

Maximum

2

Scope

per-stack

Control of whether Programmed I/O is used instead of DMA for small packets:

• 0 - no (use DMA)
• 1 - use PIO for small packets if available (default)

  Mode 1 will fall back to DMA if PIO is not currently available.

• 2 - use PIO for small packets and fail if PIO is not available.

  Mode 2 will fail to create the stack if the hardware supports PIO but PIO is not currently available.

On hardware that does not support PIO there is no difference between mode 1 and mode 2.

In all cases, PIO will only be used for small packets (see EF_PIO_THRESHOLD) and if the VI's transmit queue is currently empty. If these conditions are not met DMA will be used, even in mode 2.