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ZLP / PKTEND problem | Cypress Semiconductor

ZLP / PKTEND problem

Summary: 1 Reply, Latest post by Madhu Sudhan on 09 Mar 2016 07:30 AM PST
Verified Answers: 0
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daveb1's picture
13 posts


I have a FPGA streaming data into a FX3 GPIF in 8-bit mode. I'm using a single 32K DMA buffer which fills and transfers the data via USB to my application which has constantly has 32 x 128K reads queued. This works great while data is streamed from the FPGA. However, trouble begins when there's a pause in the data. After detecting a timeout (>5ms) the FPGA pulses PKTEND, waits 125us before checking if the stream has resumed.

When the stream does resume, each of the queued 32 x 128K reads succeed but then fail when they're re-queued. The FLAGA line goes low to indicate PC not ready and the only way to get out of this is to reset the FX3. If I keep everything the same but don't pulse PKTEND on a timeout then there is no problem (the PC isn't able to read the data queued prior to the timeout though).

Any ideas what's happening here ?




mady's picture
Cypress Employee
964 posts


Does the same issue occur with the CYpress Streamer Application. Are you following the approach as in the streamer source code?


- Madhu Sudhan

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