Lpc2000

--- In lpc2000@yahoogroups.com, Herbert Demmel <dh2@d...> wrote:
>
> >What do you need the external data bus for?  I (and many others)
> >have simulated an external data bus by just bit-banging the GPIO
> >ports.  You don't get the same performance, but you can still get
> >quite fast for most intents and purposes.  This is particularly
> >useful on the LPC213x or LPC214x because of the inexpensive
> >processor.  I, for example, have an external 2MB sram chip hooked 
> >to GPIO ports.  You can also use serial flash, for example the
> >M25P40.
> 
> I agree, BUT: Try to hook a display controller like Epson's 
> S1D13A05 to a 64 pin LPC214x and keep free enough pins for some 
> other I/O :-(
> 
> Besides that, in this case bus speed becomes an issue when you 
> imagine that you want to write 320x240 color pixels with 16 bit
> per pixel, especially when you go up to 640x40 pixels ...

I have an SED13305 hooked up via GPIOs, and it's not that bad 
performance.  Granted, I'm not doing full motion video, but what 
type of performance are you looking for?  If you don't need to do 
video then you can still bitbang it fine.

As for GPIO availability, that's why the 74HC373 was invented :)  I 
have 3 of those in my design, which makes it quite convenient for 
getting additional GPIO pins (again, provided that you don't need 
that high performance for them).  In most cases things like chip 
selects and LEDs this can work quite well with an external latch.