Boot Mode pins provide means to select the boot mode and options before the device is powered up. After every POR, they are the main source to populate the Boot Parameter Tables. See Section 4.4, Boot Parameter Tables for table list and description.
Boot mode pins can be divided into the following categories:
- MCU_BOOTMODE[02:00] – Denote system clock frequency (WKUP_HFOSC0) to ROM code for PLL configuration.
- MCU_BOOTMODE[05:03] – Select the requested boot (primary) mode after POR, that is, the peripheral/memory to boot from. These are the only pins which direct boot on MCU Only boot mode
- MCU_BOOTMODE06 – MCU Only boot mode. In MCU Only boot, ROM code skips BOOTMODE pins and attempts boot only from MCU peripherals
- MCU_BOOTMODE[09:08] – These pins can select tests to be performed on power-up (POST). POST runs in hardware, before the ROM code starts
- BOOTMODE0 – This pin allows for additional primary boot modes to be selected when in non-MCU Only (normal) mode
- BOOTMODE[3:1] – Select the backup boot mode, that is, the peripheral/memory to boot from, if primary boot device failed.
- BOOTMODE[6:4] – These pins provide optional configurations for primary boot and are used in conjuction with the boot mode selected. See Section 4.3.2.3 and the corresponding boot mode section.
- BOOTMODE7 – This pin provides optional configurations for the backup boot devices. See Section 4.3.2.4 and the corresponding boot mode section.
Note: It is user's responsibilty to set the boot mode pins (via pullups or pulldowns, and jumpers/switches) depending on the desired boot scenario.
System board must provide means to switch bootmode pin settings easily. In a field design, some pins may be hardcoded to 0 or 1 only after a careful evaluation (for example, if using MCU Only pin = 1).
Note: CTRLMMR_WKUP_DEVSTAT[23:16] register reflects the BOOTMODE pin values sampled after MCU_POR release.
CTRLMMR_WKUP_DEVSTAT[9:0] register reflects the MCU_BOOTMODE pin values sampled after MCU_POR release.