A bootloader for the Infineon C5xx series would be nice. If your memory only consists of two flash memory chips, you could preprogram one flash chip with bootloader code and map it to the upper 32K of memory. Also preprogram your program memory chip and map it to the lower 32K. When you want to ISP program, jump to the program memory location 8000h. Place your ISP bootloader code there (it will be located at 0000h on the flash chip). When your are done with ISP, jump to 0000h to restart your new code.

Here is a quick and dirty schematic to show the mapping I am talking about:



Note that this approach requires you to have a bootloader loaded on one flash chip, and code to enter the bootloader on the other chip. Once these chips are (properly) preprogrammed, they can be soldered directly to your board. From there you can ISP to your heart's content. Just be careful not to corrupt the bootloader.

Does this suit what you are trying to accomplish?

- Lee