MMC JTAG/SWD cable can't be used when P3V3 is off and the AFC is inserted in the crate
When P3V3 is off, the IC46 connects the AMC_TDI/TDO/TCK/TMS JTAG signals to MMC_TDI/TDO/TCK/TMS preventing an external debugger from accessing the MMC microcontroller through J9.
To fix it, the IC46 OE signal must be driven low high when P3V3 is off and J9 is connected.