On Thu, 14 May 1998 15:51:05 +1000, you wrote:

>1. What about a 'battery-backup' pin, so you could keep the file
>registers alive while the rest of the device was powered off.
You can already do this with sleep mode
>2. In addition to this what about a real-time clock, that could also run
>while the rest of the chip is off, using two pins for a crystal.
The 74 and others can already pretty much do this with the timer
oscillator option
>3. If no battery-backup pin, how about more chips with on-board data
>EEPROM? It's so useful, how hard is it to put it on all chips?
Probably difficult on OTPs. but not on flash based chips, which we
could certainly do with more of! 
>4. How about just making a standard 14bit core, with full program
>memory, full RAM, 8 UARTS, 8 PWM, 16kB data EEPROM...etc.  The core
>could be placed in any package with any pin count.  The connection of
>I/O to individuals pins would be by multiplexer bits set during
>programming.  The common core would be mass produced, all that needs to
>be specified is the pin count and package type.  
>A similar thing would
>happen for 12 bit cores, and so on...
>This would allow for such wonderful concepts as 3 UARTS on a 12C508 (8
>pin) package.  
You could implement 3 uarts in software reasonably easily if speed
isn't too critical, although interrupts would help.
Doing an all-in-one die would cost too much - chip cost is dominated
by die size and test cost, both of which would be high with a complex
chip. The cost of making chips doesn't reduce much with volume once
you get over a few wafers.
>Why should a 40 pin device have a UART but not an 8 pin?
The die wouldn't fit in the package!. I'm told this was the reason for
tyhe 12C508's biggest flaw - its lack of a brownout detector.
>How is pin count related to the features available?
It isn't directly, but if you look at a range of applications, you
tend to find that most  complex apps need more peripherals AND more
pins - remember Microchip determines what to make by what people want
to buy. The fact that MCT make so many different PICs illustrates that
it must be economic to do different die for even slightly different
feature sets  
>5. A few more MHz on the clock.
That's always been the case with every CPU, and will probably never
change! 
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