Lpc2000

--- In lpc2000@yahoogroups.com, "pitstock_kiwi" <keith@...> wrote:
>
> 
> Bit addressing can be a lot simpler than all the stuff I have seen 
so 
> far.
> 
> Firstly the LPC214X.H is missing the byte access registers. Why 
write 
> 32 bit address unless you need to? Also why use the old (slower) 
> legacy port IO? FAST IO should be the standard from what I see.
> 
> Use this line to turn on your fast ports unless you have some 
reason 
> to use the old stuff.
> SCS |= 0x00000003; // enable FIQ on port 0 and 1
> 
> I have an led on port 0.20 so heres the initialisation for it
> 
> // LED on port 0.20, 0x10 
> FIO0DIR2 |= 0x10;   // Led pin as output
> FIO0MASK2 |= ~0x10;  // Led masked for use
> FIO0SET2 |= 0x10;   // turn on led
> 
> And heres how I toggle the port
> 
>   if (FIO0PIN2 & 0x10){  // if led is on    Same as if (P0_20 == 1)
>    FIO0CLR2 |= 0x10;}   // turn off led.   Same as  P0_20 = 0;
>   else{
>    FIO0SET2 |= 0x10;}   // turn on led    Same as  P0_20 =1;
> 
> Because we have masked only one bit it could be even simpler if we 
> want
>    FIO0SET2 = 0xFF;   // turn on led
>    FIO0CLR2 = 0x00;   // turn off led    
> 
> Hope this helps
> Kiwi Keith
> 
> 
> Heres what I added to the LPC214X.H so I could byte access the 
port 
> as the UM10139_1.pdf mentioned
> 

This is indeed a simpler approach than the version I posted. 

The version I use has the advantage of being able to use the same 
include file (for register definitions) for both assembler and 'C': 
the MACRO is used to get the "volatile" and type correct. It's a 
fairly minor advantage, though: the clarity of the above version is 
probably preferable.

On your other points, most hardware registers on the LPC2000 series 
are 32-bit wide as far as I know. In any case, even if they're not, 
there's no advantage (that I'm aware of) to accessing them as bytes. 
Finally, I used the "old style" I/O port access simply because that 
was the example I had to hand. As others have pointed out, they have 
certain advantages (no need for read/modify/write), but you clearly 
you should use whatever's easiest/most suitable.

Brendan