User Guide

Troubleshooting Guidelines 2
82350B Installation and Configuration Guide 43
The default behavior of the 82350 driver is to use
Polling mode for transfers of 256 bytes or less and
to use Interrupt mode for larger transfers. You can
modify this default behavior by doing the following:
SICL: The SICL ihint(id, hint) function can be
called to modify the read/write behavior for on a
SICL session. The hint values allowed are:
1 I_HINT_DONTCARE (default value) Use
Interrupt mode for transfer requests larger than
256 bytes, otherwise, use Polling mode.
2 I_HINT_USEPOLL Use the Polling mode.
3 I_HINT_IO Use the Interrupt mode.
VISA: The VISA viSetAttribute(vi, VI_ATTR_
DMA_ALLOW_EN, attrValue) function can be
called to modify the read/write behavior for a VISA
session. The VI_ATTR_DMA_ALLOW_EN values
allowed are:
• VI_TRUE (default value) Use Interrupt mode
for transfer requests larger than 256 bytes,
otherwise, use Polling mode.
• VI_FALSE Use the Polling mode.
Some additional factors to consider are:
• The settings discussed above are per session.
This means you can open multiple sessions to
a device and set different transfer modes for
different sessions. The actual mode used will
then depend on which session you are using
for the read/write calls.
• In both SICL (with hint =
I_HINT_DONTCARE) and VISA (with
VI_ATTR_DMA_ALLOW_EN = VI_TRUE), the
size of the read request (as specified by
bufsize in a SICL iread() or count
in a VISA viRead() function call) will
determine the mode used even if the number
of bytes actually read is less.