59 lines
1.5 KiB
C++
59 lines
1.5 KiB
C++
|
/*
|
||
|
|
Emulate an 8 bit DAC (eg: SAM card) which writes unsigned byte
|
||
|
|
data written to its IO area to the audio buffer (as used by the speaker).
|
||
|
|
This merges the data with the speaker stream, reducing the volume
|
||
|
|
of the Apple speaker when active.
|
||
|
|
|
||
|
|
Riccardo Macri Mar 2015
|
||
|
|
*/
|
||
|
|
#include "StdAfx.h"
|
||
|
|
|
||
|
|
#include "AppleWin.h"
|
||
|
|
#include "Memory.h"
|
||
|
|
#include "DAC.h"
|
||
|
|
#include "Speaker.h"
|
||
|
|
|
||
|
|
//
|
||
|
|
// Write 8 bit data to speaker. Emulates a "SAM" speech card DAC
|
||
|
|
//
|
||
|
|
|
||
|
|
|
||
|
|
static BYTE __stdcall IOWrite_DAC(WORD pc, WORD addr, BYTE bWrite, BYTE d, ULONG nCyclesLeft)
|
||
|
|
{
|
||
|
|
// Emulate audio from an 8 bit DAC
|
||
|
|
// only if using wave data
|
||
|
|
// uses the existing speaker for the timing but then
|
||
|
|
// substitutes the analog data which gets subsequently
|
||
|
|
// sent to audio out
|
||
|
|
|
||
|
|
byte mb_res;
|
||
|
|
|
||
|
|
if (soundtype == SOUND_WAVE)
|
||
|
|
{
|
||
|
|
// use existing speaker code to bring timing up to date
|
||
|
|
mb_res = SpkrToggle(pc, addr, bWrite, d, nCyclesLeft);
|
||
|
|
|
||
|
|
// 8 bit card WAV driver (scaled by 256)
|
||
|
|
// 0xFF 255 0x7f 127
|
||
|
|
// 0x80 128 0x00 0
|
||
|
|
// 0x7f 127 0xFF -1
|
||
|
|
// 0x00 0 0x80 -128
|
||
|
|
|
||
|
|
// replace regular speaker output with 8 bit DAC value
|
||
|
|
// regular speaker data still audible but muted until speaker
|
||
|
|
// goes idle
|
||
|
|
|
||
|
|
g_nSpeakerData = (d ^ 0x80) << 8;
|
||
|
|
g_quieterSpeaker = 1;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
mb_res = MemReadFloatingBus(nCyclesLeft);
|
||
|
|
|
||
|
|
return mb_res;
|
||
|
|
}
|
||
|
|
|
||
|
|
void ConfigureDAC(LPBYTE pCxRomPeripheral, UINT uSlot)
|
||
|
|
{
|
||
|
|
RegisterIoHandler(uSlot,IO_Null,IOWrite_DAC,IO_Null,IO_Null, NULL, NULL);
|
||
|
|
}
|