Hi,
I am trying to get a custom board working with the OMAP-L138 and Micron mDDR, but it is failing the VTP IO Buffer calibration. We had originally hooked up the DDR_VREF and DDR_ZP pins incorrectly, but now corrected it so that DDR_VREF is connected to a resistor divider and DDR_ZP is connected to a 50Ohm resistor to ground. The VTP calibration never completes, with the READY bit in the VTPIO_CTL register always reading NOT_READY.
I have tried both my own startup code and the GEL file for the ZOOM OMAP-L138 EVM development kit, with the same results. Both methods do work on the EVM board, but not on our custom board. Is there anything else I can look at to troubleshoot the VTP calibration? From the documentation and the Wiki, it appears that the only things needed for VTP calibration are the peripheral clocks to the DDR2/mDDR and the 50Ohm resistor on DDR_ZP. Are there other dependencies that could cause the VTP calibration to fail?
Thanks,
Sam