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Table 13-3. Configuration Fields for the Kinetis Bootloader (continued)
Offset
Size (bytes)
Configuration Field
Description
0x1F
1
pad byte
N/A
0x24
4
Reserved
-
0x28
8
Reserved
-
0x30
4
Reserved
-
0x34
12
Reserved
-
NOTE
The flash sector containing the BCA should not be located in
the execute-only region, because the Kinetis bootloader cannot
read an execute-only region.
The first configuration field 'tag' is a tag value or magic number. The tag value must be
set to 'kcfg' for the bootloader configuration data to be recognized as valid. If tag-field
verification fails, then the Kinetis Bootloader assumes that the flash is not initialized and
uses a predefined default configuration. The tag value is treated as a character string, so
bytes 0-3 must be set as shown in the table.
Table 13-4. tag Configuration Field
Offset
tag Byte Value
0
'k' (0x6B)
1
'c' (0x63)
2
'f' (0x66)
3
'g' (0x67)
The flags in the clockFlags configuration field are enabled if the corresponding bit is
cleared (0).
Table 13-5. clockFlags Configuration Field
Bit
Flag
Description
0
HighSpeed
Enable high speed mode (i.e., 48 MHz).
1 - 7
Reserved
13.3.3 Start-up Process
Any of the following conditions will force the hardware to start the Kinetis Bootloader:
• FOPT [7] is set to 1. This forces the ROM to run out of reset.
Chapter 13 Kinetis ROM Bootloader
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
177