User`s guide

PCIS-DASK Application Hints • 45
5.3 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 5.3.1.
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 5.3.2 to 5.3.5
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.