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MicroBlaze instruction insert overrun when running no-OS SW on KCU105 out of DDR4 with FMCDAQ2 reference design

Question asked by beamer.ce1 on Oct 26, 2016
Latest reply on Nov 1, 2016 by CsomI



I currently have successfully built the FMCDAQ2 reference design project for the KCU105 evaluation kit and attempting to run the no-OS SW (2016_r1 release) on the MicroBlaze out of the on-board DDR4 SDRAM.


My Xilinx SDK project compiles with no errors but when I attempt to run the project out of DDR SDRAM I receive the following error:

   Error while launching program:  MicroBlaze instruction insert overrun.


However, if update my linker file (lscript.ld) to have all the software sections use the internal Block RAMs (BRAMs) instead of the external DDR4 SDRAM memory, the software runs as expected.  I switched to use BRAMs based on another post from someone else in the FPGA Reference Designs area who was having see the same MicroBlaze instruction insert overrun error.  But, after they switched to using BRAMs and their software was running they never followed up on any determination on why using the SDRAMs failed in the first place.


Anyone know why the software run fine out of BRAMs but fail when attempting to run out of SDRAM?  Any feedback would be appreciated.


- Brad