Re : Fastest way to transfer data from RT to FPGA

[JensG]

Hi,

my questions are simple.

1.) Which ist the fastes way to transfer data (numeric, boolean) from and to a working FPGA on a RT-PXI-system.

I've got a deterministic rt-loop and i have to write and to read data to and from a FPGA.

FPGA-DMA-FIFO or FPGA-Read/Write-"Control" or Global Var. or ...? The transfer have to be in nano/microseconds!

2.)What is the fastest way to transfer data between a rt-loop and a lower priority loop (network communication)?

RT-FIFO (1 element) or Notifier or Global Var. or Func. Var (LV2 Var.) or ...? The transfer have to be in micro/milliseconds!

Thanx to you

JensG

[BenjaminR]

Hi,

1) DMA significantly enhances RIO hardware for applications such as buffered intelligent data acquisition, streaming digital communication devices, and in-vehicle data acquisition.

2) About passing data between Normal Priority and Time-critical loop the best way is to use RT FIFO or Shared Variable FIFO.

[JensG]

Hi BenjaminR,

thanx for you answer.

to 2.) But i think a Shared Var. (with or without FIFO) are very slowly. A Global Var. is much faster. Okay, with more problems, but faster.

I need a very fast data-transfer.

Anyway thanx!

JensG

[BenjaminR]

Hi,

Using global variables in time-critical priority VIs in LabVIEW Real-Time can compromise determinism. A global variable is a shared resource. If one piece of code accesses a global variable, no other piece of code can access the global variable until the first piece releases the global variable. When you block the access of a time-critical VI to a global variable, forcing the time-critical VI to wait, you introduce jitter to the application and compromise the determinism of the application. You can avoid this behaviour by using a Functional Global, setting it to subroutine priority, and selecting the ‘Skip Subroutine Call if Busy’ option for it. With a Functional Global, the time-critical VI does not have to access the global if another section of code is already using the global. You avoid the delays caused by accessing standard global variables.