Separate machine detection from crt0 and put it in get_tv

libsrc/atari7800/get_tv.s

@@ -1,26 +1,63 @@
 ;
-; Stefan Haubenthal, 2007-01-21
+; Karri Kaksonen, 2022-03-25
 ;
-; unsigned char get_tv (void);
-; /* Return the video mode the machine is using */
+; unsigned char get_tv (void)
 ;
+	.include	"atari7800.inc"
+	.export		_get_tv
 
-        .include        "atari7800.inc"
-        .include        "get_tv.inc"
-        .importzp       tmp1, tmp2
-	.import		_paldetected
+.segment	"DATA"
 
-;--------------------------------------------------------------------------
-; _get_tv
+_paldetected:
+	.byte	$FF
 
-.proc   _get_tv
+; ---------------------------------------------------------------
+; unsigned char get_tv (void)
+; ---------------------------------------------------------------
 
-        lda	_paldetected
-	beq	ntsc
-	lda	#TV::PAL
-	rts
-ntsc:
-	lda	#TV::NTSC
+.segment	"CODE"
+
+.proc	_get_tv: near
+
+.segment	"CODE"
+
+	ldx     #$00
+	lda     #$FF
+	cmp     _paldetected
+	bne     L8
+L1:	lda     $0028
+	and     #$80
+	bne     L1
+L2:	lda     $0028
+	and     #$80
+	beq     L2
+L3:	lda     $0028
+	and     #$80
+	bne     L3
+	lda     #$00
+	sta     M0001
+	jmp     L5
+L4:	sta     $0024
+	sta     $0024
+	dec     M0001
+L5:	lda     $0028
+	and     #$80
+	beq     L4
+	lda     M0001
+	cmp     #$78
+	bcc     L6
+	lda     #$00
+	jmp     L7
+L6:	lda     #$01
+L7:	sta     _paldetected
+	ldx     #$00
+L8:	lda     _paldetected
 	rts
 
+.segment	"BSS"
+
+M0001:
+	.res	1,$00
+
 .endproc
+