Lpc2000

----- Original Message ----- 
From: "Peter Jakacki" <peterjak@...>
To: <lpc2000@yahoogroups.com>
Sent: Monday, April 11, 2005 2:49 AM
Subject: Re: [lpc2000] Re: port timing


> 
> Update frequency is not the same as output frequency when toggling. If 
> you turn the outputs on and off at an update rate of 7.4MHz you will end 
> up with a output frequency of 3.7MHz.
> 
> I run my 2106 at 22.1184MHz (overclocked) x3 and achieve an update 
> frequency of ~8.3MHz or update period of 120ns on the GPIO pins. This is 
> reading from RAM and writing shifted data. Toggling the pins would only 
> give me a ~4.15MHz signal.
> 
> Philips might wonder how important is I/O speed really, what's all the 
> gripe about. I'd say it isn't important, -except- for embedded real-time 
> control. Now which market did Philips intend these chips for?
> 
> With the 2106 I generate 192x480x8 VGA graphics over 640x480 60Hz timing 
> without any extra hardware other than some resistors. I really wish 
> Philips would listen and improve the GPIO interface, how hard can it 
> really be??? Surely it would have to be THE simplest fix.

It's inherent in the ARM architecture, nothing to do with Philips.

Leon