AR# 35245: MIG Spartan-6 MCB - User Interface cannot send commands until calibration completes (cal_done asserts)
MIG Spartan-6 MCB - User Interface cannot send commands until calibration completes (cal_done asserts)
The MIG Spartan-6 FPGA MCB design completes a calibration procedure upon reset. During this time, any commands sent from the User Interface are ignored and lost. The commands are not queued until calibration completes. Because of this, users must design their data/command generation such that no commands are requested until cal_done asserts.
The cal_done signal is an output of the top-level rtl generated by MIG ("example_design/rtl/example_top.v/.vhd" or "user_design/rtl/core_name.n.vhd"). Ensure user logic waits for cal_done = 1 before requesting any reads/writes.
The MIG design starting in v3.5 (available with ISE 12.2) will store any commands requested by the user and complete the requests once calibration completes.