Hi Rikard,

Rikard Bosnjakovic wrote:
> On 02/04/2008, Dario Greggio <adpm.to@inwind.it> wrote:
>
> [...]
>   
>>  Probably the "3 Reads" method takes less code and is reliable enough
>>  once the platform is known.
>>     
>
> It's working now. I have not pin-pointed the error, but after setting
> bit 1 of TXSTA the code works. But, another question arrived:
>   
I dont understand: bit 1 of TXSTA (TRMT) is a read-only bit! Maybe you 
wanted to write "testing"?
> void send(char letter) {
>    TXREG = letter;
>    while (!TRMT) {
>        // Delay until sent
>    }
> }
>
> works fine, but according to Nicola this is a Bad Idea (albeit I have
> yet not enough knowledge about the USART-module to tell why) and that
>   
In a general case  when you need to use any resource then you must be 
sure that it is free.
Secondly there are no reasons to wait after you have sent a byte! The 
program flow can go on.
> I should have written the function like this:
>
> void send(char letter) {
>    while (!TRMT) {
>        TXREG = letter;
>    }
> }
>   
This also is wrong! You are waiting that the port become free and 
simultaneously using it! Try this:
    while (!TRMT) ;
    TXREG = letter;

>
> Doublechecking the datasheet regarding this bit and register, Nicola
> are certainly right about it - that you have to wait for the the bit
> (indicating TSR is empty or not) to be set ("register empty") _prior_
> to setting TXREG.
>
> But, this does not work for my circuit. That is, doing it the "wrong"
> way makes it works, and doing it the "correct" way makes it not works.
>
> Now I'm entirely out in the blue and have no clue of what's going on.
>
>   
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