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SBC tests and code fix

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This commit is contained in:
jborza 2019-04-26 10:44:57 +02:00
parent b53eef7d91
commit e40450a740
2 changed files with 45 additions and 11 deletions
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11
cpu.c
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@ -129,20 +129,17 @@ void JMP(State6502 * state, word address) {
void SBC(State6502 * state, byte operand) {
//subtract operand from A
word operand_word = operand;
//borrow 0x100 from the carry flag if set
if (state->flags.c == 1) {
operand_word += 0x100;
state->flags.c = 0;
}
word result_word = state->a - operand_word;
//borrow the complement of carry flag - if the carry flag is 1, borrow 0 and vice versa
word result_word = state->a - operand_word - !state->flags.c;
byte result = result_word & 0xFF;
// overflow flag if the the result doesn't fit into the signed byte range -128 to 127
state->flags.v = ((state->a ^ operand) & 0x80) && ((state->a ^ result) & 0x80);
state->a -= result;
state->a = result;
state->flags.n = is_negative(state->a);
state->flags.z = state->a == 0;
state->flags.c = result_word > 0xFF;
}
void ADC(State6502 * state, byte operand) {

45
test6502.c
View File

@ -51,8 +51,9 @@ void test_cleanup(State6502 * state) {
State6502 create_blank_state() {
State6502 state;
clear_state(&state);
state.memory = malloc(4096);
memset(state.memory, 0, sizeof(byte) * 4096);
const int memory_size = 65536;
state.memory = malloc(memory_size);
memset(state.memory, 0, sizeof(byte) * memory_size);
return state;
}
@ -2022,6 +2023,42 @@ void test_SBC_IMM_carry() {
test_cleanup(&state);
}
void test_SBC_IMM_(byte a, byte c, byte operand, byte expected_a, byte expected_n, byte expected_z, byte expected_c, byte expected_v) {
State6502 state = create_blank_state();
state.a = a;
state.flags.c = c;
char program[] = { SBC_IMM, operand };
memcpy(state.memory, program, sizeof(program));
//act
test_step(&state);
//assert
assertA(&state, expected_a);
assert_flag_n(&state, expected_n);
assert_flag_z(&state, expected_z);
assert_flag_c(&state, expected_c);
assert_flag_v(&state, expected_v);
}
void test_SBC_IMM_multiple() {
//A, C, OP => A, N, Z, C, V
test_SBC_IMM_(0x08, 0, /* OP */ 0x01, /*A*/ 0x06, /*N*/ 0, /*Z*/ 0, /*C*/ 0, /*V*/ 0); //regular subtraction without carry bit
test_SBC_IMM_(0x08, 1, /* OP */ 0x01, /*A*/ 0x07, /*N*/ 0, /*Z*/ 0, /*C*/ 0, /*V*/ 0); //regular subtraction with carry bit
test_SBC_IMM_(0x0A, 1, /* OP */ 0x0A, /*A*/ 0x00, /*N*/ 0, /*Z*/ 1, /*C*/ 0, /*V*/ 0); //zero
test_SBC_IMM_(0x04, 1, /* OP */ 0x06, /*A*/ 0xFE, /*N*/ 1, /*Z*/ 0, /*C*/ 1, /*V*/ 0); //borrow from carry bit - 4 + 256 - 6 = 255
test_SBC_IMM_(0x04, 0, /* OP */ 0x06, /*A*/ 0xFD, /*N*/ 1, /*Z*/ 0, /*C*/ 1, /*V*/ 0); //borrow from carry bit - 4 + 256 - 6 = 254
//source: http://www.righto.com/2012/12/the-6502-overflow-flag-explained.html
//C7 - carry, B - Borrow, S7 - N, V - V
test_SBC_IMM_(0x50, 0, /* OP */ 0xF0, /*A*/ 0x60, /*N*/ 0, /*Z*/ 0, /*C*/ 0, /*V*/ 0); //Unsigned borrow but no signed overflow
test_SBC_IMM_(0x50, 1, /* OP */ 0xB0, /*A*/ 0x60, /*N*/ 0, /*Z*/ 0, /*C*/ 0, /*V*/ 1); //Unsigned borrow and signed overflow
test_SBC_IMM_(0x50, 0, /* OP */ 0x70, /*A*/ 0xE0, /*N*/ 1, /*Z*/ 0, /*C*/ 0, /*V*/ 0); //Unsigned borrow but no signed overflow
test_SBC_IMM_(0x50, 1, /* OP */ 0x30, /*A*/ 0x20, /*N*/ 0, /*Z*/ 0, /*C*/ 1, /*V*/ 0); //No unsigned borrow or signed overflow
test_SBC_IMM_(0xD0, 0, /* OP */ 0xF0, /*A*/ 0xE0, /*N*/ 1, /*Z*/ 0, /*C*/ 0, /*V*/ 0); //Unsigned borrow but no signed overflow
test_SBC_IMM_(0xD0, 1, /* OP */ 0xB0, /*A*/ 0x20, /*N*/ 0, /*Z*/ 0, /*C*/ 1, /*V*/ 0); //No unsigned borrow or signed overflow
test_SBC_IMM_(0xD0, 0, /* OP */ 0x70, /*A*/ 0x60, /*N*/ 0, /*Z*/ 0, /*C*/ 1, /*V*/ 1); //No unsigned borrow but signed overflow
test_SBC_IMM_(0xD0, 1, /* OP */ 0x30, /*A*/ 0xA0, /*N*/ 1, /*Z*/ 0, /*C*/ 1, /*V*/ 0); //No unsigned borrow or signed overflow
}
// ADC
void test_ADC_IMM_exec(byte a, byte c, byte operand, byte expected_a, byte expected_n, byte expected_z, byte expected_c, byte expected_v) {
@ -2095,7 +2132,7 @@ fp* tests_txs_tsx[] = { test_TXS, test_TSX };
fp* tests_php_plp[] = { test_PHP, test_PLP };
fp* tests_jmp[] = { test_JMP, test_JMP_IND, test_JMP_IND_wrap };
fp* tests_cmp[] = { test_CMP_ABS_equal, test_CMP_ABS_greater, test_CMP_ABS_greater_2, test_CMP_ABS_less_than, test_CPX_ABS, test_CPY_ABS };
fp* tests_sbc[] = { test_SBC_IMM };
fp* tests_sbc[] = { test_SBC_IMM_multiple };
fp* tests_adc[] = { test_ADC_IMM_multiple };
fp* tests_bit[] = { test_BIT_multiple };
@ -2107,9 +2144,9 @@ void run_suite(fp * *suite, int size) {
}
void run_tests() {
RUN(tests_sbc);
RUN(tests_bit);
RUN(tests_adc);
RUN(tests_sbc);
RUN(tests_lda);
RUN(tests_ora);
RUN(tests_and);