/*
 *   external.c
 *
 *   This file is part of Emu48
 *
 *   Copyright (C) 1995 Sebastien Carlier
 *
 */
#include "pch.h"
#include "Emu48.h"
#include "ops.h"

//| 38G  | 39G  | 40G  | 48SX | 48GX | 49G  | Name
//#F0E4F #80F0F #80F0F #706D2 #80850 #80F0F =SFLAG53_56

// memory address for flags -53 to -56
#define SFLAG53_56	(  (cCurrentRomType=='6')								\
	                 ? 0xE0E4F												\
					 : (  (cCurrentRomType=='A')							\
					    ? 0xF0E4F											\
					    : (  (cCurrentRomType!='E' && cCurrentRomType!='X')	\
					       ? (  (cCurrentRomType=='S')						\
					          ? 0x706D2										\
						      : 0x80850										\
						     )												\
						   : 0x80F0F										\
					      )													\
					   )													\
					)

static __inline VOID Return(CHIPSET* w)
{
	w->rstkp=(w->rstkp-1)&7;
	w->pc = w->rstk[w->rstkp];
	w->rstk[w->rstkp] = 0;
	return;
}

VOID External(CHIPSET* w)					// Beep patch
{
	BYTE  fbeep;
	DWORD freq,dur;

	freq = Npack(w->D,5);					// frequency in Hz
	dur = Npack(w->C,5);					// duration in ms
	Nread(&fbeep,SFLAG53_56,1);				// fetch system flags -53 to -56

	w->carry = TRUE;						// setting of no beep
	if (!(fbeep & 0x8) && freq)				// bit -56 clear and frequency > 0 Hz
	{
		if (freq < 37)   freq = 37;			// low limit of freqency (NT)
		if (freq > 4400) freq = 4400;		// high limit of HP (SX)

		if (dur > 1048575)					// high limit of HP (SX)
			dur = 1048575;

		Beep(freq,dur);						// NT: ok, Windows 95: default sound or standard system beep

		// estimate cpu cycles for beeping time (2MHz / 4MHz)
		w->cycles += dur * ((cCurrentRomType=='S') ? 2000 : 4000);           

		// original routine return with...
		w->P = 0;							// P=0
		w->intk = TRUE;						// INTON
		w->carry = FALSE;					// RTNCC
	}
	Return(w);
	return;
}