User`s manual

Application Hints 55
PCIS-DASK
Digital Input Programming Hints
4.3 Digital Input Programming Hints
The PCIS-DASK provides two types of digital input operation: non-
buffered single-point digital input operation and buffered continu-
ous 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 .
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 (in Windows
®
NT) or during Windows startup (in Win-
dows
®
98). It is recommended that the applications use the
DI_InitialMemoryAllocated function to get the size of initially allo-
cated memory before performing continuous DI operation.
The buffered continuous analog input includes synchronous con-
tinuous DI, non-double-buffered asynchronous continuous DI and
double-buffered asynchronous continuous DI. These are
described in section to section section. For special consideration
and performance issues for the buffered continuous analog input,
refer to Chapter 5: Continuous Data Transfer.