Lpc2000

rseku wrote:

>Thank You very much indeed!
>Meantime I figured out, that external interrupt trigerring by level 
>keeps triggering as long as the reason is kept.This makes continous 
>interrupt processing the way, that other processes are completly blocked.
>I hardly ever can imagine reason for such implementation?!
>  
>

Yes, some external interrupt controllers / sources exert a continuous 
active level until all interrupt sources within them have been cleared.  
A device commonly found on early PC motherboards comes to mind, the 
InTel 8259 interrupt controller, a very popular chip.

There are advantages to the level activated interrupts, unfortunately, 
they did not implement the other advantage which is Edge triggering.

Look at the LPC2138 part, the External Interrupts are handled 
differently, at least you have the option of chosing Edge vs Level 
triggering.

Lucky for me that my customer fscked the original controller spec so 
badly that I had to put the MMC on the LPC2138 instead of the LPC2106.  
Now I have the Card Detect line on one of the edge triggerable External 
Interrupts.  It is now possible to detect when the card is removed / 
inserted.

TomW

-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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