Agilent Technologies Agilent 82350B - Manual (Page 33)

Installing and Configuring the 82350B 1
82350B Installation and Configuration Guide 21
Set 82350B Read/Write Performance Mode
The 82350B card read and write calls use 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 82350B 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.