User`s guide

30 ? PCIS-DASK Application Hints
buffered continuous digital output operation and pattern generation.
The non-buffered single-point DO uses software polling method to write data to the device. The programming scheme
for this kind of DO operation is described in section 4.4.1.
The buffered continuous DO uses DMA transfer method to transfer data from user’s buffer to device. The maximum
number of count in one transfer depends on the size of initially allocated memory for digital output 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 DO_InitialMemoryAllocated function to get the size of initially allocated memory before
start performing continuous DO operation.
The buffered continuous digital output includes synchronous continuous DO and asynchronous continuous DO. They
are described in section 4.4.2 and 4.4.3 section individually. About the special consideration and performance issues for
the buffered continuous digital output, please refer to the Continuous Data Transfer in PCIS-DASK chapter for the
details.
The Pattern Generation DO outputs digital data pattern repeatedly at a predetermined rate. The programming scheme
for this kind of DO operation is described in section 4.4.4.