SPRUJD3A July 2025 – October 2025 F28E120SB , F28E120SC
During boot-up, the boot ROM initializes the device clocking, depending upon the reset source, to assist in faster boot time response. Clock configurations are performed by the boot ROM code only for POR and XRS reset types. For all other resets, the boot ROM starts executing with the clocks that were already set up before reset.
| Source | Frequency | Description |
|---|---|---|
| WROSCDIV8 | 2.5MHz to 8.75MHz | Default clock source |
| SYSOSCDIV4 | 8MHz | Alternate clock source |
| HPLL | 160MHz |
Boot ROM configures to use PLL output clock. This can be skipped (bootROM to use SYSOSC) by configuring TI OTP. |
| Reset Source | Clock State |
|---|---|
| POR/XRS |
1. Use SYSOSC 2. Modify the SYSDIVSEL based on TRIM (TI OTP) configuration (minimum divider is /1). 3. Power up PLL and set an integer multiplier. Check PLL Lock status and put PLL output in clock path – This is gated by OTP config as well to make sure successful boot on fresh parts on bench. 4. After PLL output is enabled in clock path, CPU is executing at PLLOUT/SYSCLKDIV (can be configured using TRIM (TI OTP)) frequency. |
| All other Resets | Maintain clocks setup before device reset. |