Function Call in ST

READ_SD(EN := EN_SD_READ,
     ATTRIB := ATTRIB_SD_READ,
     FILENO := FILENO_SD_READ,
     SEG := SEG_SD_READ,
     FORMAT := FORMAT_SD_READ,
     NVAR := NVAR_SD_READ,
     ADRVAR := ADRVAR_SD_READ);
DONE_SD_READ := READ_SD.DONE;
ERR_SD_READ := READ_SD.ERR;
ERNO_SD_READ := READ_SD.ERNO;