Does then, the C420 have a serial programing port? What is the MAX232A for?

The big reoson I'm using a C390 is, I got two of them for free. I don't know if I could get the C420 for free from Maxim, or wether internal flash would be worth the getting it sent to me.

I just got a sample, to get some diverisfication in the IC's I get from Maxim. It's not like I knew what I was exactly geting.

When I go over the C390 data sheets I get rather intimidated. It looks different then the Atmel 8052's that I use. More complicated. But it says things about pin for pin campatibility with some chips.