Lpc2000

42Bastian Schick wrote:

>Adam Malinowski schrieb:
>  
>
>>Nice uC. Unfortunately it hasn't MMU but it's still seems to be good 
>>product.
>>    
>>
>
>I'd say most embedded applications do not need an MMU.
>
>  
>
As long as you don't use malloc() and free() in your software, no, there 
is no need for it.  However, the MMU allows you to compress your heap 
and make the "holes" appear as a larger segment instead of a lot of tiny 
ones scattered about.  Memory fragmentation can also be a big issue with 
an embedded system.

The other advantage would be to virtualize large arrays of structures 
onto Flash memory devices such as Secure Digital or Compact Flash.  
Having a miniscule 32K of RAM is a PITA.  I have an array of structures 
which are 72 bytes in size and one element of that struct is a 48 char 
text field.  This text field is only needed for the initial report but 
must be kept if the system is told to 're-report all events'.  Since I 
have 100 structures, that is 7K of data.  of which, 4K is something that 
could be stored on a disk drive.  Virtualization could allow me to 
extend the "RAM" and hold that infrequently accessed data in slower memory.

No, an MMU would be a distinct advantage in an LPC2138 or ...... (insert 
your favorite LPC2000 chipname).

I would like to see something like an MMU in a LPCx000 processor.  It 
would be nice if the MMU could be powered down via PCONP if it is not 
needed...

Regards,

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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