AVR-Chat

Hi,

did not realize that you needed the port toggle and I agree that is a
significant weekness of ARM-peripheral bus. Most devices in the market
have the ports connected to the peripheral bus, ergo, some slow
toggle. Exception (although I am biased ;-)) the Atmel SAM7. This
device connects the ports to the AHB bus. Don't know exactly how much
fast the ports are (don't have HW) but the calculations come down to
approx, 2x the frequency of the LPC2000 running at the same clock.
Because these devices are limited to 50 MHz, you could probably get in
the neighborhood of 7 MHz at the ports. 

It is only a matter of time until one or more manufacturers address
this weekness by connecting the ports (or at least some fast pins) to
the local bus. This would enable the ports to be switched I think at
CPU-clock / 4. Still the AVR is better with CPU/2 BUT you get so much
more benefits with the ARM.

The AVR is great for I/O tasks and running it at 8 MHz with similar
I/O performance as an ARM with 60 MHz is also a lot more power
efficient. So for I/O intensive tasks lots of bit reading and
toggeling a 32-bit might be inappropriate.

For now, your best bet if looking at ARM would be the SAM7 for fast
ports, 6 months from now I guess that will be different.

Bob

--- In AVR-Chat@yahoogroups.com, "leon_heller" <leon.heller@d...> wrote:
> 
> --- In AVR-Chat@yahoogroups.com, Jon Hylands <jon@h...> wrote:
> > On Tue, 8 Feb 2005 09:05:18 -0000, "Paul Maddox"
> > <P.Maddox@s...> wrote:
> > 
> > > Its a really BIG shame as I had several uses for it, but I'm 
> sorry the IO is
> > > just absurdly slow.
> > > A waste of, potentially, a great chip!
> > 
> > Is that a general property of the ARM7 chips, or something specific 
> for
> > that Philips board?
> 
> It's inherent in the ARM architecture, the APB (Advanced Peripheral 
> Bus) which is generally used for ordinary I/O is simple but very 
> slow. The AHB (Advanced High-performance Bus) is much faster and a 
> lot more complicated.
> 
> Leon