GCFR Global Control Function Register. 0x40005800 0x00 0x400 registers REG0 Register 0. 0x00 read-write CKPDRV Hyperbus CKP Drive Setting. 0 4 CKNDRV Hyperbus CKN Drive Setting. 4 4 RDSDLL_EN Hyperbus RDS DLL Enable. 8 1