Chapter 6 Double Buffer Mode Principle - ADLINK Technology cPCI-7200 User Manual

6
Double Buffer Mode Principle
The data buffer for double-buffered DMA DI operation is a circular buffer
logically. It logically divided into two equal halves. The double-buffered DI
begins when device starts writing data into the first half of the circular buffer
(Figure 6-1a). After device begins writing to the second half of the circular
buffer, you can copy the data from the first half into the transfer buffer (Figure
6-1b). You now can process the data in the transfer buffer according to
application needs. After the board has filled the second half of the circular
buffer, the board returns to the first half buffer and overwrites the old data. You
now can copy the second half of the circular buffer to the transfer buffer (Figure
6-1c). The data in the transfer buffer is a gain available for process. The
process can be repeated endlessly to provide a continuous stream of data to
your application (Figure 6-1d).
a
Incoming DMA
input data
c
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52 Double Buffer Mode Principle
Circular Buffer
Transfer Buffer
> >
Empty Buffer
b
d
Untransferred Data
Figure 6-1
> > >
> > >
Transferred Data