User`s manual

42 Application Hints
PCIS-DASK
Analog Input
4.1 Analog Input
PCIS-DASK provides two kinds of analog input operation: nonbuf-
fered single-point analog input readings and buffered continuous
analog input operation.
The non-buffered single-point AI uses software polling method to
read data from the device.
The buffered continuous analog input uses interrupt transfer or
DMA transfer method to transfer data from device to user's buffer.
The maximum number of count in one transfer depends on the
size of initially allocated memory for analog input in the driver. The
driver allocates the memory at system boot (in Windows
®
NT) or
Windows startup time (in Windows
®
98). It is recommended that
the AI_InitialMemoryAllocated function be used to get the size of
initially allocated memory before performing continuous AI opera-
tion.
The buffered continuous analog input includes:
X synchronous continuous AI
X non-triggered non-double-buffered asynchronous continu-
ous AI
X non-triggered double-buffered asynchronous continuous AI
X triggered non-double-buffered asynchronous continuous AI
X triggered double-buffered asynchronous continuous AI
These are described in section to section . For special consider-
ation and performance issues for the buffered continuous analog
input, refer to Chapter 5: Continuous Data Transfer.