SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
Table 4-13 shows configuration pins assignment to functions when No-boot/Dev-boot was selected. In this mode, ROM code is bypassed and user is allowed to run his own code for development or debug.
MCU-only mode is not compatible with no-boot/dev-boot since the DebugSS is in the main domain.
BOOTMODE Pins | Field | Value | Description | MCU Only=1 Value |
---|---|---|---|---|
6 | Split | 0 | Split/Lockstep configuration of MCU R5 cores derived from efuse | N/A |
1 | MCU R5 cores forced to split mode | |||
5 | Arm/Thumb | 0 | ARM mode reset vectors | N/A |
1 | Thumb mode reset vectors | |||
4 | No/Dev | 0 | Development Boot | N/A |
1 | No boot |
During the Development boot (BOOTMODE[4] = 0), the DMSC ROM code will act as if boot of the primary image has completed, and the DMSC ROM then will be waiting for a firmware load message from MCU R5. Thus user you can load a standard u-boot/SPL image to the R5 RAM. U-boot/SPL will then load the DMSC firmware and complete the full boot.
In No-boot (BOOTMODE[4] = 1), both the DMSC and MCU R5 ROMs are bypassed and both CPUs are held in a dummy branch-to-self loop. No-boot is the most minimal device touch state by the ROM - only minimal hardware configurations are done and none of the PLLs is locked/configured. No-boot is suitable if user wants to load his own PLL, Pad config, and other basic settings.