Erase block should be erased before rewrite

Hi,

There is an issue in the code writing a ROM.
You can't write twice at the same place on the flash. You need to erase the corresponding erase-block (the flash is divided in 128K erase-blocks) before a rewrite.

See https://github.com/mikeryan/ems-flasher/blob/master/Tech for details (or contact me).

Christophe.

[Stewmath]

I'm guessing this is only an issue with my multirom support? I don't use it very frequently anymore, preferring to not have a menu, so perhaps I could have missed such a bug. Single roms appear to work fine.

Given that Mike Ryan has multirom support in his version now, this fork seems redundant. So I'm not terribly motivated to fix the issue, especially given my very limited understanding of the protocols. I appreciate the bug report, though.