Interrupt problem with write buffers

berndsirozynski — Tue, 02 Jan 2018 15:15:52 GMT

!!! never clear Interruptflags at the last line of interrupt function

One time more, i have found that the LPC serie has a big timing problem if clearing interrupt flags .

This problem only occures if you clear the Interrupt flag at the very last line of your interrupt function

and additional you set the compiler optimization to -O3

The processor needs time to clear the internal interrupt flag, but before the interrupt flag

was cleared we get a next interrupt.

This problem i have found in the LPC1768 and LPC1347

To solve the problem you need only a litte bit time or you clear the interruptflag

NOT at the very last line.

Now i always put the "DSB" instruction after clearing the interrupt flag in my functions.

In my currently project i get a I2C interrupt and the status ist 0xF8

this is an mismatch status and not described in the manual.

i think the error is an result of the internal write buffers of the CPU.

if i use one of the following action it works fine.

i think this behavior must described in the user manual.

Re: Interrupt problem with write buffers

soledad — Tue, 02 Jan 2018 21:27:36 GMT

Hi,

Thank you for your feedback, we will check this issue.

Regards

Soledad