Omega Vehicle Security DAQ-16 - Manual (Page 21)

2.7 Direct Memory Access
Direct Memory Access (DMA) transfers provide a way of transferring data from the
DAQ-16's A/D converter into the computer's memory without using the Central Processing
Unit (CPU). DMA capability enables other system software to be executed while data is being
input from the DAQ-16.
The DAQ-16 actually implements two DMA channels. The advantage of having two DMA
channels is that one channel can be transferring data while the second channel is being
programmed. When the first channel is finished, the second channel will automatically take
over and continue the data transfer. The first channel can then be re-programmed while the
second channel is transferring data. In this way, the DAQ-16 can acquire data continuously
until terminated by the user.
The DAQ-16 supports 16-bit DMA transfers on channels 5, 6, and 7. The DMA channel(s) are
selected by jumpers J8 and J9 as shown in Figure 2-10.
DRQ7
DACK7
DRQ6
DACK6
DRQ5
DACK5
DRQ6
DACK6
DRQ7
DACK7
DRQ5
DACK5
J8 J9
DMA Channel 1 DMA Channel 2
Figure 2-10. Jumpers J8 and J9 Configuration
WARNING: To properly implement the DMA capability, the DRQ and DACK of each
DMA channel must be jumpered to the same number, i.e. DRQ 5/DACK 5. If both DMA
channels are to be used, each channel must be jumpered to a different number, i.e. channel
1 is jumpered to DRQ 5 /DACK 5 and channel 2 is jumpered to DRQ 7/DACK 7.
DAQ-16 Users Manual 21