These cards use a combination of IRQ and DMA depending on the availabilty (it is done behind the scene). Obviuosly, for buffered output DMA is used.
"Can the DC value be updated anytime or at the end of a buffer ?"
These are updated the moment the values are outputed. In my work I never noticed any delay.
"Could you also generate to buffered acquisition on the same AO (say channels 0..4 for one buffer and 5..7 for the other under different timing conditions) ?"
You can generate buffered output on more than one channel group (is there a maximum? I do not know).
"under different timing conditions"
If you mean different frequencies ? Yes, but this acheived by placing more than one cycle per buffer for one group (yo
u will have frequency F on one group, and frequency XF on the other group) where X is the number of cycles per buffer. It is the same update clock in the card that is used. (therefore, they are not really independent).
The ATAO -10 card has two indepedent clocks where you can have one set at a particlular frequency with an update rate from clock 1, and the other set from clock 2. (If I remember correctly, channels 0-7 use one clock,8,9 use the other clock). Then you can generate truely two independent signals. Obviously, you cannot use the ATAO with DAQ MX, and because it is an ISA board, you will not have a use for it any more. I used it when ISA was king.
I think NI has released new AO card that has more than one clock ( the PCI 6722 is not the one).
