Hello,
I'm a new embedded develloper , the AT91sam9
chips(for examples ,the at91sam9rl64) datasheet explain the
boot program mechanism that "The Boot Program integrates different programs that manage download and/or upload into the different memories of the product". I want to ask that what the Boot Program is,what's the relationship between Bootstrap and the boot program . Is the boot program exit on the internal rom , and can not be erased by software(or a Firmware)?
Thanks for your answer.

ROMBoot, as the name implies, resides in ROM. It searches memory devices for AT91BootStrap, or equivalent, code to copy and run in SRAM. The exact order this occurs is typically described in the chip manual for the part being used.

The internal ROM can be replaced by external code, typically in NOR Flash and attached to the EBI, by using the BMS pin.