Information

28.4.11.10 Read Once Command
The Read Once command provides read access to a reserved 64-byte field located in the
program flash IFR (see Program Flash IFR Map and Program Once Field). Access to this
field is via 16 records, each 4 bytes long. The Read Once field is programmed using the
Program Once command described in Program Once Command.
Table 28-56. Read Once Command FCCOB Requirements
FCCOB Number FCCOB Contents [7:0]
0 0x41 (RDONCE)
1 Read Once record index (0x00 - 0x0F)
2 Not used
3 Not used
Returned Values
4 Read Once byte 0 value
5 Read Once byte 1 value
6 Read Once byte 2 value
7 Read Once byte 3 value
After clearing CCIF to launch the Read Once command, a 4-byte Read Once record is
read from the program flash IFR and stored in the FCCOB register. The CCIF flag is set
after the Read Once operation completes. Valid record index values for the Read Once
command range from 0x00 to 0x0F. During execution of the Read Once command, any
attempt to read addresses within the program flash block containing this 64-byte field
returns invalid data. The Read Once command can be executed any number of times.
Table 28-57. Read Once Command Error Handling
Error Condition Error Bit
Command not available in current mode/security FSTAT[ACCERR]
An invalid record index is supplied FSTAT[ACCERR]
28.4.11.11 Program Once Command
The Program Once command enables programming to a reserved 64-byte field in the
program flash IFR (see Program Flash IFR Map and Program Once Field). Access to the
Program Once field is via 16 records, each 4 bytes long. The Program Once field can be
read using the Read Once command (see Read Once Command) or using the Read
Resource command (see Read Resource Command). Each Program Once record can be
programmed only once since the program flash IFR cannot be erased.
Flash Operation in Low-Power Modes
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
548 Freescale Semiconductor, Inc.