TI工程师你们好，我在使用EVM开发板测试DDR时出现如下错误，
[C66xx_0] DDR3A initialization
Initialize DDR data rate = 100.000/1*20/6*4= 1333.3 MTS, bus width = 64 bits.
DDR PHY status PGSR0=0x80000ff7.
DDR PHY Impedance Calibration is NOT done!
ddr phy阻抗校准未完成，是我如下参数配置存在问题吗
/*-----DDR Timing values from DDR memory data sheet----*/
/*the unit of following parameters is ns (nanosecond)*/
DDR_cfg.tRCD = 13.5;
DDR_cfg.tRP = 13.5;
DDR_cfg.tRAS = 36;
DDR_cfg.tRC = 49.5;
DDR_cfg.tWR = 15;
DDR_cfg.tFAW = 30;
DDR_cfg.tRFC = 160;
DDR_cfg.tWLO = 9;
/*the unit of following parameters is clock number*/
DDR_cfg.tCCD = 4;
DDR_cfg.tMRD = 4;
DDR_cfg.tDLLK = 512;
DDR_cfg.tZQOPER= 256;
DDR_cfg.tZQCS = 64;
DDR_cfg.tWLMRD= 40;
/*DDR3 timing parameters specified as maximum of nanosecond and number of clock*/
DDR_cfg.tWTR.nCK= 4;
DDR_cfg.tWTR.ns = 7.5;
DDR_cfg.tRTP.nCK= 4;
DDR_cfg.tRTP.ns = 7.5;
DDR_cfg.tXP.nCK= 3;
DDR_cfg.tXP.ns = 6;
DDR_cfg.tXPDLL.nCK= 10;
DDR_cfg.tXPDLL.ns = 24;
DDR_cfg.tXS.nCK= 5;
DDR_cfg.tXS.ns = DDR_cfg.tRFC+10;
DDR_cfg.tCKE.nCK= 3;
DDR_cfg.tCKE.ns = 5.625;
DDR_cfg.tMOD.nCK= 12;
DDR_cfg.tMOD.ns = 15;
DDR_cfg.tRRD.nCK= 4;
DDR_cfg.tRRD.ns = 6;
