Copyright © 2020
Alazar Technologies Inc.
56
ATS9353 User Manual
AutoDMA
Just having dual-ported memory or a FIFO, on its own, does not solve the
problem of capturing rapidly occurring triggers or streaming applications.
Software still has to get involved in re-arming the hardware after every capture
and again for reading the data from on-board acquisition memory.
ATS9353’s proprietary AutoDMA circuitry allows the acquisition system to be re-
armed by a hardware command and data transfer to be initiated by the
hardware itself, thus removing virtually all “in-process” software involvement.
Figure 6 - AutoDMA acquisition and transfer cycle
Of course, software still has to set up the DMA when one of the buffers fills up,
but, thanks to the custom DMA engine and fully asynchronous driver that uses
overlapped IO, these tasks can be paralleled.
In other words, when software is re-arming DMA channel 0, DMA channel 1 is
already transferring data to host memory.
Note that if data throughput is too high, a DMA_OVERFLOW flag gets set and is
available to the programmer.
Consumption of the captured data is, of course, under the control of user-
created software, and it is this that will determine the maximum PRF instead of
the bus throughput.
The important thing to note is that if asynchronous DMA is used, CPU usage is
no more than 5%, even if a
1.6 GB/s DMA is going on.