ATS9360 User Manual
39
AutoDMA
Just having a FIFO, on its own, does not solve the problem of
PRF captures 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.
ATS9360’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.
Of course, software still has to set up the DMA when one of
the buffers fills up, but, thanks to the dual-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 3.5 GB/s
DMA is going on.
ACQUIRE
ACQUIRE
ACQUIRE
ACQUIRE
TRANSFER
TRANSFER TRANSFER
