ADLINK cPCI-9116 - Manual (Page 57)

Operation Theory
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5.1.4 A/D Data Transfer Modes
After the end of the A/D conversion, A/D data are buffered into the Data FIFO
memory. The FIFO size on the 9116 series card is 1024 (1K) words. If the
sampling rate is 10 KHz, the FIFO can buffer 102.4 ms of analog signal. After
the FIFO is full, any data after this time will be lost.
The data must be transferred to the host memory after the data is ready and
before the FIFO is full. In scan acquisition mode, there are 3 data transfer
modes that can be used. They are described below.
EOC Interrupt Transfer
The 9116 series card provides traditional hardware End-Of-Conversion (EOC)
interrupt capability. Under this mode, an interrupt signal is generated when the
A/D conversion has ended and the data is ready to be read into the Data FIFO.
The hardware interrupt will be asserted and its corresponding ISR (Interrupt
Service Routine) will be invoked and executed. The ISR program can read the
converted data. This method is suitable for data processing applications under
real-time and fixed sampling rate.
FIFO Half-Full Interrupt Transfer
Sometimes, the application does not need real-time processing, cause the
foreground program is busy polling the FIFO data. The FIFO half-full interrupt
transfer mode is useful for the situation mentioned above.
Under this mode, an interrupt signal is generated when FIFO becomes half-full.
It means that there are 512 words of data in the FIFO ready for transfer. The
ISR can read the whole block of data when the interrupt occurs. A “block is 512
words long.
Note: In the current version, EOC & FIFO half-full interrupt transfer mode
doesn’t support pre-trigger and middle-trigger mode data acquisition.
Users must use DMA transfer to work with pre-trigger or middle-trigger
data acquisition.