User`s guide

24 ? PCIS-DASK Application Hints
4.3 Digital Input Programming Hints
PCIS-DASK provides two kinds of digital input operation ? non-buffered single-point digital input operation and
buffered continuous digital input operation.
The non-buffered single-point DI uses software polling method to read data from the device. The programming
scheme for this kind of DI operation is described in section 4.3.1.
The buffered continuous DI uses 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 digital 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 DI_InitialMemoryAllocated function to get the size of initially allocated memory before performing
continuous DI operation.
The buffered continuous analog input includes synchronous continuous DI, non-double-buffered asynchronous
continuous DI and double-buffered asynchronous continuous DI. They are described in section 4.3.2 to 4.3.5 section
respectively. About the special consideration and performance issues for the buffered continuous digital input, please
refer to the Continuous Data Transfer in PCIS-DASK chapter for the details.