Lpc2000

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.

*Peter*

Gennady Palitsky wrote:

>I put on a board 17.73MHz crystal and with direct store from registers to 
>GPIO got port toggle frequency
>of ~7.6MHz. I believe that 20MHz crystal (don't have one) will give ~8.6MHz 
>toggle.
>Though extra 5 cycles at STR is still there, the port frequency is way above 
>originally mentioned 3.7MHz.
>Does it mean that something changed on LPC2138 ?
>
>