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initialize CPU correctly, never set bit 4 or 5 of P

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This commit is contained in:
Brad Grantham 2020-12-27 20:50:32 -08:00
parent c798a2d886
commit afb222f18f
1 changed files with 5 additions and 5 deletions
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10
cpu6502.h
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@ -147,15 +147,15 @@ struct CPU6502
a(0), a(0),
x(0), x(0),
y(0), y(0),
s(0), s(0xFF),
p(0x20), p(I),
exception(RESET) exception(RESET)
{ {
} }
void reset() void reset()
{ {
s = 0xFD; s = 0xFF;
uint8_t low = bus.read(0xFFFC); uint8_t low = bus.read(0xFFFC);
uint8_t high = bus.read(0xFFFD); uint8_t high = bus.read(0xFFFD);
pc = low + high * 256; pc = low + high * 256;
@ -1272,7 +1272,7 @@ struct CPU6502
} }
case 0x28: { // PLP case 0x28: { // PLP
p = stack_pull(); p = stack_pull() & ~ (B2 | B);
break; break;
} }
@ -1547,7 +1547,7 @@ struct CPU6502
} }
case 0x40: { // RTI case 0x40: { // RTI
p = stack_pull(); p = stack_pull() & ~ (B2 | B);
uint8_t pcl = stack_pull(); uint8_t pcl = stack_pull();
uint8_t pch = stack_pull(); uint8_t pch = stack_pull();
pc = pcl + pch * 256; pc = pcl + pch * 256;