SLUSB72D March 2013 – April 2021 UCD3138064
The UCD3138064 incorporates a 8 kB boot ROM. This boot ROM includes support for:
The Boot ROM is entered automatically on device reset. It initializes the device and then performs checksums on the program flash. If the first 2 kB of either program FLASH has a valid checksum, the program branches to location 0 in the appropriate Program FLASH module. This permits the use of a custom boot program. If the first checksum fails, it performs some additional checksum calculations to determine where the valid program is located. This permits full automated program memory checking, when there is no need for a custom boot program. The complete decision tree is located in Figure 9-28. "Branch to Program Flash 1" means Flash 1 is at address 0x0000, and Flash 2 is at address 0x8000. "Branch to Program Flash 2" means Flash 2 is at address 0x0000, and Flash 1 is at address 0x8000.
If neither checksum is valid, the Boot ROM stays in control, and accepts commands via the PMBus interface. These functions can be used to read and write to all memory locations in the UCD3138064. Typically they are used to download a program to Program Flash, and to command its execution.