03-06-2013 03:57 AM
On the zc702 board, by default the pinmux for the reference design assigns MIO 8 as "QSPI Feedback" signal. In the documentation, I foudn that MIO8 is supposed to be connected to the DS12 LED on the board.
What I'm seeing in practice is that BOTH cases seem to be true. When pinmuxing MIO8 as QSPI Feedback, the DS12 LED will "flicker" when the QSPI flash is active.
So my question is, how is this pin supposed to be used?
If i pinmux it to GPIO and use it as a general purpose LED, will this interfere with QSPI operation?
What does QSPI need this feedback line for? It appears to be functioning just fine if you don't mux it.
03-11-2013 09:39 AM
I observed this issue on the Early Access versions of the ZC702 board. No access to the production board. With the Early board, the MIO8 must be configured to QSPI Feedback clock function for QSPI to work. Regardless of the feedback mode of the QSPI controller itself. The QSPI controller feeds it's own clock back to itself via the MIO8. At least that's with the Early version. Sounds like it was fixed so that clock was fed back within QSPI controller and MIO8 has been freed up.
05-07-2013 09:27 AM
No longer have access to the Xilinx boards. I don't know when the bug was fixed and how to identify which silcon rev. If the bug is fixed, LED DS12 can be whatever you want it be. Out of the box, looks like DS12 is QSPI clock or a QSPI activity indicator.