moved PAL/NTSC support to a separate routine

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FeralChild64 committed 2019-10-20 16:14:54 +02:00
1 parent c41da81e06
commit 2afe11c3b3
3 files changed
+67 -60

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+1 -17
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@@ -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