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AR# 37529

Spartan-3E - Speedgrade -4 - Readback limitations - Why does my Readback have errors?


Afterusing a processor to read back the whole Spartan-3E configuration data and then comparing itto the original bit file by using the MASK file, there are some unexpected errors. There appear to be errors on my BRAM frames. What is the problem here?


The Readback feature is available in most Spartan-3E FPGA product options except in the XC3S1200E and XC3S1600E FPGAs when using the -4 speed grade in the Commercial temperature grade.

Similarly, block RAM Readback support is not available in the -4 speed grade, Commercial temperature devices. If Readback is required in an XC3S1200E or XC3S1600E FPGA, or if block RAM Readback is required on any Spartan-3E FPGA, upgrade to either the Industrial temperature grade version or the -5 speed grade.

For those devices that do not support block RAM readback, such as XC2S250E, try to avoid reading back the BRAM content and comparing it.If the design reads the whole configuration memory, one workaround is to instantiate all the BRAMs in your design, then the MASK file will mask out all the RAM bits and not compare them while performing readback verification.
AR# 37529
Date 12/15/2012
Status Active
Type General Article
  • Spartan-3E
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