1. I have read "AN12352 LPC54S0xx Execute In Place with Secure Boot"，I know that the image can be downloaded before the secure boot is turned on, but if I start secure boot , can I still program a new image?
2. If the answer of the first question is OK, then the way to start a new image after booting safely is to enter ISP mode and download it using blhost?
3. I try to use blhost to program an image to the external flash refer to the "Getting Started with LPC540xx-LPC54S0xx Flashloader User's Guide", but one of the steps failed. I failed in the process of erasing the program. I guess I have error in configuring the external flash, but I dont't know how to configure it. I think the configureation method described in th manual is difficult to understand. Is there any good advice? The following is my operation.