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Clear the decimal bit in BRK; also improve test logic for BRK

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This commit is contained in:
Peter Evans 2018-02-22 13:44:13 -06:00
parent 90892c32e4
commit e35ff91fa7
2 changed files with 7 additions and 0 deletions
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1
src/mos6502.exec.c
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@ -32,6 +32,7 @@ DEFINE_INST(brk)
mos6502_push_stack(cpu, cpu->PC & 0xff);
mos6502_push_stack(cpu, cpu->P);
cpu->P |= MOS_INTERRUPT;
cpu->P &= ~MOS_DECIMAL;
cpu->PC += 2;
}

6
tests/mos6502.exec.c
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@ -8,12 +8,18 @@ TestSuite(mos6502_exec, .init = setup, .fini = teardown);
Test(mos6502_exec, brk)
{
// Start out with the decimal bit high so we can test it gets turned
// off; this assignment also guarantees the I bit is low, and that
// should be set high by the handler as well.
cpu->P = MOS_DECIMAL;
vm_8bit orig_P = cpu->P;
cpu->PC = 123;
mos6502_handle_brk(cpu, 0);
cr_assert_eq(cpu->PC, 125);
cr_assert_eq(cpu->P & MOS_INTERRUPT, MOS_INTERRUPT);
cr_assert_eq(cpu->P & MOS_DECIMAL, 0);
cr_assert_eq(mos6502_pop_stack(cpu), orig_P);
cr_assert_eq(mos6502_pop_stack(cpu), 123);