Bootloader MCF51JM

[SecondTechCo]

I have a boot loader and an application in the MCF51 series.   Every example I see from freescale launches a  boot loader upon reset while the user is pressing a button or pin.  We dont get input from the user that way.  We want to launch the boot loader from our application.   Is there a very simple way to do this ?   We have read a lot of questions about calling a function at a fixed address but see no answers as to how to do this.  We want an extremely simple way to do this.  A byte in RAM that doesn't get rest when the process resets would be great but calling a boot loader function from our application if its in a fixed location might work to.  Any other ideas or anyone know how to do these ?

[BlackNight]

It does not have to be a button. It can be anything. Typically the bootloader just needs to have a decision point/criteria either to continue with the bootloader or with to execute the application (if present).

If I expect a user interaction, then a push button is my choice. But I have done this by other means e.g. writing a byte in a battery buffered external SRAM or RTC. You can do this with the internal microprocessor RAM too, you just need to make sure that the startup code does not clear that memory location. Another consideration could be to program a byte in FLASH memory by the application, then perfom a reset (e.g. through not serving the watchpoint).

I hope this gives some ideas.

[SecondTechCo]

Thanks. So when you reset the processor (using an untrapped error) but keep power applied, the RAM memory does not reset unless I initialize it  ?