Re: [hatari-devel] Enabling of ACIA IRQs

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

On 31/05/2013 18:53, Eero Tamminen wrote:
> Hi,
>
> On perjantai 31 toukokuu 2013, Nicolas Pomarède wrote:
> > I don't use midi, so I never really noticed.
> >
> > In midi.c Midi_Data_WriteByte(), we have :
> >
> >           if (!ConfigureParams.Midi.bEnableMidi)
> >                   return;
> >
> > So, if midi is not enabled, byte are not processed and nothing will
> > happen (including irq).
>
> I don't think 1) is really a problem.  But MIDI should work if we
> have an option for enabling it at run-time.
>
>
> > As for 2), maybe the files to communicate via midi are only opened when
> > Hatari starts, not later when you check/uncheck ? But Midi_Init()
> > already seems to be called in change.c, so I don't know what is missing.
>
> Midi_Reset() which starts the MIDI interrupt:
> -------
> void Midi_Reset(void)
> {
>          MidiControlRegister = 0;
>          MidiStatusRegister = ACIA_SR_TX_EMPTY;
>          nRxDataByte = 1;
>
>          if (ConfigureParams.Midi.bEnableMidi)
>          {
>                  CycInt_AddRelativeInterrupt(2050, INT_CPU_CYCLE,
> INTERRUPT_MIDI);
>          }
> }
> -------
>
> Is called only when emulated is reseted.
>
>
> couple of alternatives:
> 1) enabling MIDI triggers emulation reset
> 2) enabling MIDI calls Midi_Reset()
>
> 1) is probably the safer option.

yes, maybe it's possible to use 2), but it would require tests to ensure 
it doesn't break anything. At least, a forced reset will warn the user. 
We can improve later.

> I also guess the interrupt should be disabled in Midi_Reset(),
> if MIDI isn't enabled...

you can add to the above 'if' :

	else
	{
		CycInt_RemovePendingInterrupt ( INTERRUPT_MIDI )
	}

midi's int is not really pending, but it doesn't matter, it will be 
disabled.

Could you do the change ? I'm not familiar with midi to check it works.

Nicolas