Re: [hatari-devel] Enabling of ACIA IRQs

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

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.

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


	- Eero