
• AHB-AP
• Private peripheral bus
22.3 Boot
This section describes the boot sequence, including sources and options.
22.3.1 Boot options
The Flash Option (FOPT) register in the Flash Memory module (FTFE_FOPT) allows the
user to customize the operation of the MCU at boot time. The register contains read-only
bits that are loaded from the NVM's option byte in the flash configuration field. The
default setting for all values in the FTFE_FOPT register is logic 1 since it is copied from
the option byte residing in flash, which has all bits as logic 1 in the flash erased state. To
configure for alternate settings, program the appropriate bits in the NVM option byte.
The new settings will take effect on subsequent POR and any system reset. For more
details on programming the option byte, see
The MCU uses FTFE_FOPT to configure the device at reset as shown in the following
table.
Table 22-2. Flash Option Register (FTFE_FOPT) definition
Bit
Num
Field
Value
Definition
7
BOOTSRC_SEL
Boot Source Selection: these bits select the boot sources if boot pin option bit
BOOTPIN_OPT (FOPT[1]) = 1.
BOOTSRC_SEL (FOPT[7]) and BOOTPIN_OPT (FOPT[1]) value as below:
00
Boot from ROM with BOOTCFG0/NMI pin low, or Boot from Flash with
BOOTCFG0/NMI pin high
01
Boot from Flash
10
Boot from ROM
11
Boot from ROM
6
Reserved
Reserved for future expansion
5-4
Reserved
Reserved for future expansion
3
RESET_PIN_CFG
Enables/disables control for the RESET pin.
0
RESET_b pin is disabled following a POR and cannot be enabled as reset
function. When this option is selected, there could be a short period of contention
during a POR ramp where the device drives the pin low prior to establishing the
Table continues on the next page...
1. CDBGRSTREQ does not affect AHB resources so that debug resources on the private peripheral bus are available
during System Reset.
Boot
Kinetis KE1xF Sub-Family Reference Manual, Rev. 4, 06/2019
558
NXP Semiconductors
Summary of Contents for KE1xF Series
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