Re: [Amforth-devel] Interrupt handling question

[Matthias T. <mt...@we...>]

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Hans,

Hans H=FCbner schrieb:

> I am trying to port my timer interrupt driven display code to
> amforth-1.9 and have some problems with that.
>=20
> On the documentation page
> (http://amforth.sourceforge.net/interrupts.php), an example interrupt
> handler is printed:
>=20
> : doint1
>     . ( <-- this is dangerous in interrupts )
> ;
>=20
> The danger set aside (I guess the dangerous part is the fact that the
> UART will generate another interrupt that may not be properly
> handled), it seems that this example has a stack effect.

Ok, you are right. The example is a non-example. An interrupt
word must not have any stack effect.

>  Is this intended?

not really, sorry.

> Is there something on the stack that the interrupt handler
> must remove?

no. All the low level interrupt stuff is handled by amforth (namely
the reti instruction). On forth level there is no state to keep other
than the stacks.

> I am asking because my code crashes - If I leave the stack as it was
> before entering the interrupt handler, I see periodic reboots (once a
> second) when I enable the interrupt handler.

without your code it is difficult to analyze.

> If I pop the topmost
> item, amforth plain crashes with trash characters written to the
> console.

Well, that is most likly, see above.

> It could be that the new interrupt handler code is too slow
> to work with the timer interrupt,

The new code is faster then the old one.

> but before getting into debugging
> that, I'd like to know if there is something fundamentally wrong with
> my code.

you could try using a semaphore like flag to detect an interrupt
overrun.

> BTW:  Is there anything in amforth except ISTORE that writes to flash?

No, all words which write to flash call i! to do the "real work".

>  I am asking because I want to give amforth on a flashless AVR a try.

What's a flashless AVR??? Sounds like sodium free salt ;=3D)

Bye
Matthias
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