On 13/01/2012 17:29, Isaac Marino Bavaresco wrote:
> Em 13/1/2012 15:08, Andre Abelian escreveu:
>> Hi  all,
>>
>> I am testing pic32 and something simple I am having hard time to underst=
and.
>> I have 2 leds connected to G12 and G14 when I use test1 code LED1 never =
tuns on.
>> test2 and test3 is ok. my question is why test1 is not working. G12 and =
G13 are digital I/O.
>> if i use debugger step over it works.
>>
>> test1:
>> LED1 =3D 1;
>> LED2  =3D 0;
>> delay;
>> LED1 =3D0;
>> LED2=3D1;
>> delay
>>
>>
>>
>> test2:
>> if I use&  and | logic it works
>>
>> LED1 | =3D 1;
>> LED2&  =3D 0;
>> delay;
>> LED1&=3D0;
>> LED2 |=3D1;
>> delay
>>
>> test3:
>> if I use LATGSET and LATGCLR it works
>>
>> Since G12 and G14 are not analog pins and I do not have external capacit=
or I do not think this is Read modify write issue.
>> my question is do you know why test1  LED1 stays off when running.
>>
>> here is the code.
>>
>> while(1)
>> {
>>    int short_delay;
>>    uint8_t returnStatus1,returnStatus2;     // to test
>>
>>   //     led_d7_green&=3D 0;
>>   //     led_d8_green |=3D 1;
>>
>>   //     led_d7_green =3D 0;
>>   //     led_d8_green =3D 1;
>>
>>        LATGCLR =3D 0x5000;   // 0b0101000000000000;
>>        LATGSET =3D 0x1000;   // 0b0001000000000000;
>>
>>        short_delay =3D 1000*1000;     // create short delay
>>        while(short_delay--){};
>>
>>   //     led_d7_green |=3D 1;
>>   //     led_d8_green&=3D 0;
>>
>>   //     led_d7_green =3D 1;
>>   //     led_d8_green =3D 0;
>>
>>        LATGCLR =3D 0x5000;   // 0b0101000000000000;
>>        LATGSET =3D 0x4000;   // 0b0100000000000000;
>>
>>        short_delay =3D 1000*1000;     // create short delay
>>    while(short_delay--){};
>>
>>      }
>>
>> thanks
>>
>> Andre
>
> Probably related to RMW (read-modify-write). When stepping-over or
> running the code that takes more instructions, there is time for the pin
> to settle before changing the other pin.
>
> When running the faster code at full speed the first pin is read with
> its previous value and written back with the older value.
> You are writing to register PORTG, right? Try writing to register LATG
> instead.
>
>
> Best regards,
>
> Isaac
>

Sounds like RMW to me too, given that it's the first LED (in the code)=20
that doesn't turn on. For any fast port manipulations use the dedicated=20
atomic registers (as you have done with LATGSET, etc in the other test)

--=20
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