Set 82351A Read/Write Performance Mode - Keysight 82351A User Manual

1 Installing and Configuring the 82351A

Set 82351A Read/Write Performance Mode

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The 82351A card read and write calls using one of two
modes:
• Polling. Bytes are transferred to/from the card, one at a
time. Polling mode is advantageous for transferring a
small number of bytes because the setup overhead is very
low, but it does require CPU involvement for each byte
transferred.
• Interrupt. An entire buffer is transferred to/from the card
without CPU involvement. Interrupt mode is advantageous
for transferring large buffers because the higher per byte
transfer rate more than compensates for the relatively
long interrupt setup overhead.
The default behavior of the 82351A 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 either of the following:
SICL: The SICL ihint(id, hint) function can be called to
modify the read/write behavior for a SICL session. The hint
values allowed are:
• I_HINT_DONTCARE (default value) Use Interrupt mode
for transfer requests larger than 256 bytes, otherwise, use
Polling mode.
• I_HINT_USEPOLL Use the Polling mode.
• 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.
82351A User's Guide