They Seem to have ISP programmers that are not compatible with all their MCU versions, hence you'll require a number of them as you work through their array of MCU's.

Over the years, this has come up again and again. Sometimes a silicon upgrade makes a previously useful programmer unuseable. Too bad, but they're not terribly expensive.

Some manufacturers stick with a single programmer type, either by leaving their ISP hardware alone or by building their MCU's so the same progammer works with all their products. That's not easy, so everyone doesn't do it.

Beware of the tempting do-it-yourself solution. Better buy one that definitely works with the MCU version you plan to use. It's very hard to answer the question, "Is it the MCU, or is it the programmer, or is it my code?"

RE