45.4.10.9 Read Once CommandThe Read Once command provides read access to special 64-byte fields located in theprogram flash 0 IFR (see Program Flash IFR Map and Program Once Field). Access tothe Program Once field is via 16 records (index values 0x00 - 0x0F), each 4 bytes long.These fields are programmed using the Program Once command described in ProgramOnce Command.Table 45-25. Read Once Command FCCOB RequirementsFCCOB Number FCCOB Contents [7:0]0 0x41 (RDONCE)1 Program Once record index (0x00 - 0x0F)2 Not used3 Not usedReturned Values4 Program Once byte 0 value5 Program Once byte 1 value6 Program Once byte 2 value7 Program Once byte 3 valueAfter clearing CCIF to launch the Read Once command, a 4-byte Program Once record isread and stored in the FCCOB register. The CCIF flag is set after the Read Onceoperation completes. Valid record index values for the Read Once command range from0x00 - 0x0F. During execution of the Read Once command, any attempt to readaddresses within the program flash block containing the selected record index returnsinvalid data. The Read Once command can be executed any number of times.Table 45-26. Read Once Command Error HandlingError Condition Error BitCommand not available in current mode/security FSTAT[ACCERR]An invalid record index is supplied FSTAT[ACCERR]45.4.10.10 Program Once CommandThe Program Once command enables programming to special 64-byte fields in theprogram flash 0 IFR (see Program Flash IFR Map and Program Once Field). Access tothe Program Once field is via 16 records (index values 0x00 - 0x0F), each 4 bytes long.These records can be read using the Read Once command (see Read Once Command) orusing the Read Resource command (see Read Resource Command). These records can beprogrammed only once since the program flash 0 IFR cannot be erased.Chapter 45 Flash Memory Module (FTFA)KL27 Sub-Family Reference Manual , Rev. 5, 01/2016Freescale Semiconductor, Inc. 923
