Add irq handling, PAL/NTSC detection and clock()

libsrc/atari7800/crt0.s

@@ -1,16 +1,17 @@
         .export		_zonecounter
+        .export		_paldetected
         .export		 __STARTUP__ : absolute = 1
         .export		 _exit
         .import		 __ROM_START__
         .import		 __RAM3_START__, __RAM3_SIZE__
         .import		 initlib, donelib
         .import		 zerobss, copydata
+        .import		 IRQStub
         .import		 push0, _main
+        .include        "atari7800.inc"
 	.include	"zeropage.inc"
 
 INPTCTRL        =       $01
-OFFSET          =       $38
-CTRL            =       $3c
 
         .segment "STARTUP"
 start:
@@ -38,6 +39,29 @@ start:
         jsr     zerobss
         jsr     initlib
 
+	; Examine machine type as we need the info early
+vboff:	lda     MSTAT
+	bmi     vboff
+vbon:   lda     MSTAT
+        bpl     vbon
+vboff2: lda     MSTAT
+        bmi     vboff2
+        lda     #$00
+        sta     _paldetected
+        jmp     mtsta
+count:  sta     WSYNC
+        sta     WSYNC
+        dec     _paldetected
+mtsta:  lda     MSTAT
+        bpl     count
+        lda     _paldetected
+        cmp     #$78
+        bcc     mtntsc
+        lda     #$01
+        jmp     mtpal
+mtntsc: lda     #$00
+mtpal:  sta     _paldetected
+
         ; Call main program (pass empty command line)
         jsr     push0           ; argc
         jsr     push0           ; argv
@@ -50,7 +74,7 @@ _exit:
 
 NMIHandler:        
         inc     _zonecounter
-        rti
+        jmp	IRQStub
 
 IRQHandler:
         rti
@@ -58,6 +82,9 @@ IRQHandler:
         .segment "DATA"
 _zonecounter:
         .byte   0
+_paldetected:
+	.byte	0		; 0 = NTSC, 1 = PAL
+
 
         .segment "ENCRYPTION"
         .res    126, $ff        ; Reserved for encryption