LabVIEW
How to do arbitration in LabVIEW FPGA
Solved!
Hi vicky,
how we decide that which one is receiving request first out of five devices.
You read your 6 digital inputs as fast as the FPGA or the module allows, I often also read the full port (group of 8, 16 or 32 bits). Whenever one of those bits is toggled (hint: XOR function!) you know there is a "request" and you can handle this request by setting some other digital outputs…
Can we have to use case statements for all this in FPGA VI
Yes, sure.
or some other way ??
You can use many other functions and structures in a FPGA VI, even FIFOs (aka queues)…
Hi vicky,
by default the FPGA executes loops at 40MHz - or 25ns between iterations. Do you really expect more than one request in this short interval?
I assume there will be only one request per 25ns interval so you know which request occured in which iteration of your receiver loop…
@vicky2889 wrote:
yes by using XOR gate we will find there is request but how we determine which request we receive first.
Set a flag, enqueuer an element, execute a case, output a value, store the timestamp, trigger an SRQ... Thousand ways to do it.
Recommending one of them is not easy, as what makes the right choice it's highly circumstantial. E.g. it depends... On an FPGA everything usually needs to fit like a glove. Each choice made needs to fit other parts.
I am pretty sure arbitration is not required to solve the problem.
Search LabVIEW like a graph! Hi vicky,
using standard LabVIEW it looks like this:
In the FPGA you may do the ArraySearch "manually" using your own routine…
how we determine which device request we receive first.
That "first" request is the one, where the boolean value changed in an earlier iteration then the "second" one…
You need to take into account the loop iterations between the comparison of your digital inputs!
