moved PAL/NTSC support to a separate routine

c64/kernal/init/fda3.ioinit.s

@@ -8,6 +8,7 @@
 // CPU registers that has to be preserved (see [RG64]): none
 //
 
+
 IOINIT:
 
 	// Set $00/$01 port mode and value
@@ -75,22 +76,6 @@ IOINIT:
 	sta CIA2_ICR
 	sta CIA1_ICR
 
-	// Set timer interval to ~1/60th of a second
-	
-	// Probably NTSC is the default one, as PAL support was introduced later,
-	// in a patch - see [CM64] page 242 and page:
-	// - http://commodore64.se/wiki/index.php/Commodore_64_KERNAL_ROM_versions
-	// "The KERNAL ROM R1 was obviously used only in early NTSC systems. It lacks the PAL/NTSC detection"
-
-	// NTSC C64 (https://codebase64.org/doku.php?id=base:cpu_clocking),
-	// is clocked at 1.022727 MHz, so that 1/60s is 17045 CPU cycles
-
-	ldy #<17045
-	ldx #>17045
-
-	sty CIA1_TIMALO
-	stx CIA1_TIMAHI
-
 	// Enable timer interrupt
 	lda #$81
 	sta CIA1_ICR
@@ -117,4 +102,3 @@ IOINIT:
 
 	// Set IEC bus to its initial idle state
 	jmp iec_set_idle
-

c64/kernal/init/ff5b.cint.s

@@ -11,46 +11,4 @@
 CINT:
 
 	jsr cint_legacy
-
+	jmp setup_pal_ntsc
-cint_check_pal_ntsc:
-
-	// Detect video system (PAL/NTSC), use Graham's method, as it's short and reliable
-	// see here: https://codebase64.org/doku.php?id=base:detect_pal_ntsc
-
-	lda VIC_RASTER
-!:
-	cmp VIC_RASTER
-	beq !-
-	bmi cint_check_pal_ntsc
-
-	// Result in A, if no interrupt happened during the test:
-	// #$37 -> 312 rasterlines, PAL,  VIC 6569
-	// #$06 -> 263 rasterlines, NTSC, VIC 6567R8
-	// #$05 -> 262 rasterlines, NTSC, VIC 6567R56A
-
-	cmp #$07
-	bcc cont_done
-
-cint_pal:
-
-	// (This value was calculated by running a custom IRQ handler on a C64
-	// with original KERNAL, and writing the values of $DC04/5 to the screen
-	// in the IRQ handler to see roughly what value the timers must be set to)
-	// ldy #<16380
-	// ldx #>16380
-
-	// PAL C64 (https://codebase64.org/doku.php?id=base:cpu_clocking),
-	// is clocked at 0.985248 MHz, so that 1/60s is 16421 CPU cycles
-
-	ldy #<16421
-	ldx #>16421
-
-	sty CIA1_TIMALO
-	stx CIA1_TIMAHI
-
-	lda #$01
-!:
-	sta TVSFLG
-
-cont_done:
-	rts

c64/kernal/init/setup_pal_ntsc.s

@@ -0,0 +1,65 @@
+
+// Detect video system (PAL/NTSC), use Graham's method, as it's short and reliable
+// see here: https://codebase64.org/doku.php?id=base:detect_pal_ntsc
+
+
+setup_pal_ntsc:
+
+	lda VIC_RASTER
+!:
+	cmp VIC_RASTER
+	beq !-
+	bmi setup_pal_ntsc
+
+	// Result in A, if no interrupt happened during the test:
+	// #$37 -> 312 rasterlines, PAL,  VIC 6569
+	// #$06 -> 263 rasterlines, NTSC, VIC 6567R8
+	// #$05 -> 262 rasterlines, NTSC, VIC 6567R56A
+
+	cmp #$07
+	bcc setup_ntsc
+
+	// FALLTROUGH
+
+setup_pal:
+
+	// Set timer interval to ~1/60th of a second
+
+	// (This value was calculated by running a custom IRQ handler on a C64
+	// with original KERNAL, and writing the values of $DC04/5 to the screen
+	// in the IRQ handler to see roughly what value the timers must be set to)
+	// ldy #<16380
+	// ldx #>16380
+
+	// PAL C64 (https://codebase64.org/doku.php?id=base:cpu_clocking),
+	// is clocked at 0.985248 MHz, so that 1/60s is 16421 CPU cycles
+
+	ldy #<16421
+	ldx #>16421
+
+	lda #$01
+
+	// FALLTROUGH
+
+setup_pal_ntsc_end:
+
+	sty CIA1_TIMALO
+	stx CIA1_TIMAHI
+
+	sta TVSFLG
+
+	rts
+
+setup_ntsc:
+
+	// Set timer interval to ~1/60th of a second
+	
+	// NTSC C64 (https://codebase64.org/doku.php?id=base:cpu_clocking),
+	// is clocked at 1.022727 MHz, so that 1/60s is 17045 CPU cycles
+
+	ldy #<17045
+	ldx #>17045
+
+	lda #$00
+
+	beq setup_pal_ntsc_end // branch always