Why does the Intel® Stratix® 10 HBM2 IP calibration success signal stay low at Tj less than 0°C ?

The minimum operating temperature for HBM2 DRAM is 0°C. When the Intel® Stratix® 10 MX FPGAs must be configured at less than 0°C, the HBM2 controller will read the junction temperature (Tj) using the TSD (temperature sense diode) and will hold the controller in reset.  The local_cal_success signal and AXI_*_ready signals won't be asserted until Tj reaches 0°C or greater.