Ok, let's just get right to it. (novel to follow, sorry)

I am trying to choose a microcontroller for a project. I estimate I will need ~8K of data space and ~8K of code space (?). The data space cannot be ROM, I must be able to add to it indefinitely.

I am doing my prototyping with an evaluation board (MacKenzie's SBC-51) but I am getting the distinct impression that this won't last much longer because it appears as though the best way to use external flash memory is to get rid of the evaluation board and allow the 8051 to do all of the hard work for you. (I had been trying to send the addresses, handshaking signals, and data through the 8155 on the board, all through software and that has NOT been a pleasant experience.)

I decided today to calculate the amount of data space I thought I would need for the lifetime of the device and I estimated 4k so I doubled that (because I have been eaten by that monster before) to 8K. I am positive I can fit my program in LESS than 8k so I figure I need about 16K of total memory space. So I thought Cool, I can get by without using external memory! (maybe)

The question is: If a chip says it has 16K of internal flash memory, can I use that for whatever I want to use it for or am I stuck using it for JUST code? Also, if the data sheet says the chip is "in system programmable through serial port", does that mean I would have to hook lines up from the microcontroller TO the microcontroller to program the memory space? Or does this mean something else entirely? (I am speaking specifically of the DS89C420 here but I have also looked at the 80C51 from Phillips and several Atmel chips)

One last question. In the real world, do you find one company that you like and stick with their chips or do you look around for the best chip to suit your needs and suffer through the data sheets? I keep getting overwhelmed with data sheets boasting six billion interrupts and single cycle instruction execution and all of these other things but I am finding it difficult to glean the information regarding how much and what kind of memory space is available from these data sheets. Is there some kind of database out there that will allow me to quickly compare the most important aspects of each chip?

Any help is greatly appreciated and I will be happy to supply more information if I have not been clear.

AN