You would have thought that the whole point of microcontrollers was to decrease the number of different chips that have to be manufactured on the basis of them being programmable.
I've used microcontrollers extensively so I'm not just randomly rambling ;)
Here's examples of differences:
- Power consumption (some applications care less, some care more).
- Number of pins. Sometimes you just need one input and one output, shoving a high pin count device in there doesn't make sense.
- Pin functions. Higher current capability or other specialized functions like A/Ds D/As etc.
- On-board peripherals. Some microcontrollers have on-board motor controllers, networking, specialized counter hardware, real time clocks, DSP blocks etc.
- Integrated memory and types of memory.
- Oscillator options/frequencies.
Add to that all the different CPU architectures and vendors.
It's more like the microcontroller replaces a bunch of chips or custom chips in certain applications. It's less like you can build one microcontroller to rule them all. Those are still generally mass produced devices so there's really not a lot of economy of scale, i.e. the one micro to do everything (if that was even possible, which it is not) would just be more expensive and less optimized.
