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More details in the ADC test

This commit is contained in:
Peter Evans 2018-04-30 23:00:21 -05:00
parent de34d7d0f9
commit ab022c5d58
1 changed files with 72 additions and 14 deletions
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86
tests/mos6502/arith.c
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@ -6,23 +6,85 @@
TestSuite(mos6502_arith, .init = setup, .fini = teardown);
/*
* ADC is a deceptively simple instruction. It works like this:
*
* A = A + DATA + C
*
* If D = 1, then ADC works in an entirely different manner, treating
* the input as BCD (Binary-Coded Decimal).
*
* Z = 1 if RESULT = 0
* N = 1 if RESULT has BIT 7 high
* V = 1 if (A ^ DATA) has BIT 7 high AND (A ^ RESULT) has BIT 7 high
* C = 1 if (16-BIT) RESULT > 0xFF
*/
Test(mos6502_arith, adc)
{
cpu->A = 5;
mos6502_handle_adc(cpu, 3);
cr_assert_eq(cpu->A, 9);
cpu->A = 0xfe;
mos6502_handle_adc(cpu, 0x5);
cr_assert_eq(cpu->A, (vm_8bit)(0xfe + 0x5));
vm_8bit start = 30,
main = 60,
ztest = 0x100 - start,
vtest = 0x80,
ctest = 0xff;
// Test with and without carry
cpu->P |= MOS_CARRY;
cpu->A = start;
mos6502_handle_adc(cpu, main);
cr_assert_eq(cpu->A, start + main + 1);
cpu->P &= ~MOS_CARRY;
cpu->A = 9;
mos6502_handle_adc(cpu, 64);
cr_assert_eq(cpu->A, 73);
cpu->A = start;
mos6502_handle_adc(cpu, main);
cr_assert_eq(cpu->A, start + main);
cr_assert_eq(cpu->P & MOS_ZERO, 0);
cr_assert_eq(cpu->P & MOS_NEGATIVE, 0);
cr_assert_eq(cpu->P & MOS_OVERFLOW, 0);
cr_assert_eq(cpu->P & MOS_CARRY, 0);
// If an add results in Z = 1, it necessarily implies C = 1. Say you
// have A = 1, and add -1. With two's complement, the binary coded
// form of -1 is 0xff; thus 0xff + 0x1 = 0x100, or 0x00 after
// variable overflow, and thus C = 1.
//
// NOTE: variable overflow is e.g. when you go from 0xff to 0x00; it
// means something different from the V/OVERFLOW status in the 6502
// chip, which cares about going from a positive to a negative, or
// from a negative to a positive.
cpu->A = start;
cpu->P &= ~MOS_CARRY;
mos6502_handle_adc(cpu, ztest);
cr_assert_eq(cpu->A, 0);
cr_assert_eq(cpu->P & MOS_ZERO, MOS_ZERO);
cr_assert_eq(cpu->P & MOS_NEGATIVE, 0);
cr_assert_eq(cpu->P & MOS_OVERFLOW, 0);
cr_assert_eq(cpu->P & MOS_CARRY, MOS_CARRY);
// We can test both negative and overflow here. We could do a
// separate test on the N flag if we set A = 0x80 and added a small
// number, like 0x3; we would essentially begin with a negative
// number and end with a negative number.
cpu->A = start;
cpu->P &= ~MOS_CARRY;
mos6502_handle_adc(cpu, vtest);
cr_assert_eq(cpu->A, start + vtest);
cr_assert_eq(cpu->P & MOS_ZERO, 0);
cr_assert_eq(cpu->P & MOS_NEGATIVE, MOS_NEGATIVE);
cr_assert_eq(cpu->P & MOS_OVERFLOW, MOS_OVERFLOW);
cr_assert_eq(cpu->P & MOS_CARRY, 0);
cpu->A = start;
cpu->P &= ~MOS_CARRY;
mos6502_handle_adc(cpu, ctest);
// Cast to vm_8bit since we're working with variable overflow
cr_assert_eq(cpu->A, (vm_8bit)(start + ctest));
cr_assert_eq(cpu->P & MOS_ZERO, 0);
cr_assert_eq(cpu->P & MOS_NEGATIVE, 0);
cr_assert_eq(cpu->P & MOS_OVERFLOW, 0);
cr_assert_eq(cpu->P & MOS_CARRY, MOS_CARRY);
// This should handle decimal mode without complaint
cpu->P |= MOS_DECIMAL;
cpu->P &= ~MOS_CARRY;
cpu->A = 0x18;
mos6502_handle_adc(cpu, 0x3);
cr_assert_eq(cpu->A, 0x21);
@ -270,8 +332,6 @@ Test(mos6502_arith, inx)
ntest = 0x7F,
ztest = 0xFF;
vm_16bit addr = 0x123;
cpu->addr_mode = ACC;
mos6502_handle_inx(cpu, main);
cr_assert_eq(cpu->X, main + 1);
@ -297,8 +357,6 @@ Test(mos6502_arith, iny)
ntest = 0x7F,
ztest = 0xFF;
vm_16bit addr = 0x123;
cpu->addr_mode = ACC;
mos6502_handle_iny(cpu, main);
cr_assert_eq(cpu->Y, main + 1);