Why does SPI indirect programming fail in multiple SPI daisy chains for Spartan-6 FPGA configurations?
Why does iMPACT fail to load the indirect SPI CORE for programming in SPI daisy chains for Spartan-6 FPGA configurations?
This issue occurs when you have multiple Spartan-6 FPGA devices in SPI Daisy Chain configuration mode with DONE pins tied together.
While doing SPI Indirect Programming, iMPACT fails programming because the Slave FPGA drives the DONE signals LOW (as expected) while the Master is configured with the CORE file from iMPACT to begin the SPI indirect programming.
The work-around is to configure the Slave FPGA first, so that DONE is released when iMPACT configures the Master FPGA.
The other work-around is to add a hardware switch to isolate the master FPGA's DONE pin for indirect programming only.