Hi, zhou
Everytime system power up, boot ROM will be always running first, then it will call plugin to init power, DRAM...there is a file linux.bd in linux-bootlets, I think you can put your test image here, then call it and run it. But you still need to program it into NAND flash, and set system to boot from NAND, then ROM will try to read the image in NAND and run it in DRAM, not sure whether this is what you want.....