Thanks for this. It is what I have been trying to do next. I have a short routine that sets up the UART, timers and interrupts, and these are the only registers I am changing from defaults. I have reset all of these to power-on state (and turned on ENBOOT) but then a jump to 0xF800 causes a reset. I will double check all the other registers that I may be interfering with and try again.

I have been looking at the bootloader source for the 'CC01 from ATMEL, but I am suspicious. On the batch of chips we have the bootloader version is 1.1.2, but the source refers to 1.4 and later. There are two interesting things I have noticed- first, the entry point seems to be 0xFC00, but it's not clear. Second, the code does depend on previous state (which is defined on reset, but must be forced if I jump from my app).

Anyway, any further suggestions would be appreciated. I can't believe I am the only person who wants to be able to do this.

Andy