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Enter bootloader
Init hardware
Load user-config
data
Configure clocks
Init Flash,
Property and
Memory interfaces
Is
BootPin
asserted to
boot from
ROM?
Is user
application
valid?
Disable Timeout
detection
Enable Timeout
Check and enable
Timeout value
Shutdown all
Peripherals
Is
Timeout Check
enabled and
has Timeout
occurred?
SPIn entered
interrupt state?
I2Cn entered
interrupt state?
Ping packet
received on
LPUARTn?
Shutdown unused
Peripherals
Jump to user
application
Enter bootloader
state machine
No
Yes
No
No
No
Yes
No
Yes
Yes
Yes
Has
Has
Was a
Use the enablePeripheral field
in user config data to enable (or
not) LPUARTn (or SPIn or I2Cn
or USB).
Init LPUARTn,
SPIn, I2Cn and USB
activity
detected on
USB?
No
Was
Yes
No
Is
direct boot
valid?
No
Yes
Figure 13-2. Kinetis Bootloader Start-up Flowchart
Chapter 13 Kinetis ROM Bootloader
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
179