User`s guide

PCIS-DASK Application Hints ? 15
4.1 Analog Input Programming Hints
PCIS-DASK provides two kinds of analog input operation ? nonbuffered 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 programming
scheme for this kind of AI operation is described in section 4.1.1.
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 time (in Window NT) or Windows startup time
(in Window 98). We recommend the applications use AI_InitialMemoryAllocated function to get the size of initially
allocated memory before performing continuous AI operation.
The buffered continuous analog input includes:
- synchronous continuous AI
- non-triggered non-double-buffered asynchronous continuous AI
- non-triggered double-buffered asynchronous continuous AI
- triggered non-double-buffered asynchronous continuous AI
- triggered double-buffered asynchronous continuous AI
They are described in section 4.1.2 to 4.1.6 section respectively. About the special consideration and performance
issues for the buffered continuous analog input, please refer to the Continuous Data Transfer in PCIS-DASK chapter for
the details.