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RTI implementation fix - applying the status register

This commit is contained in:
jborza 2019-05-04 16:03:54 +02:00
parent 80b1af1a30
commit 4186df1468
2 changed files with 41 additions and 3 deletions
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7
cpu.c
View File

@ -291,7 +291,12 @@ void RTS_(State6502 * state) {
void RTI_(State6502 * state) {
//interrupt pushes PC first, then status register
//RTI should pull status register and program counter from the stack
byte sr = pop_byte_from_stack(state);
byte value = pop_byte_from_stack(state);
//we don't read the BRK flag
value &= ~(1 << 4);
//the bit 5 always comes in as true
value |= 1 << 5;
memset(&state->flags, value, sizeof(Flags));
word address = pop_word_from_stack(state);
state->pc = address;
}

37
test6502.c
View File

@ -1881,7 +1881,7 @@ void test_PHP() {
test_cleanup(&state);
}
void test_PLP_no_flags() {
void test_PHP_no_flags() {
//initialize
State6502 state = create_blank_state();
//no flags are set
@ -2360,6 +2360,37 @@ void test_branching_multiple() {
test_branch(BVS_REL, /*N*/ 0, /*V*/ 0, /*Z*/ 0, /*C*/ 0, /*EXP_PC*/0x02);
}
// RTI
void test_RTI() {
State6502 state = create_blank_state();
state.sp = 0xfc;
//arrange
char program[] = { RTI };
memcpy(state.memory, program, sizeof(program));
state.memory[0x1FF] = 0x12; //return address
state.memory[0x1FE] = 0x34; //return address
state.memory[0x1FD] = 0x80; //only flag n should be set
//act
test_step(&state);
//assert
assert_sp(&state, 0xFF);
assert_pc(&state, 0x1234);
assert_flag_c(&state, 0);
assert_flag_d(&state, 0);
assert_flag_b(&state, 0);
assert_flag_z(&state, 0);
assert_flag_v(&state, 0);
assert_flag_n(&state, 1);
assert_flag_i(&state, 0);
//cleanup
test_cleanup(&state);
}
/////////////////////
typedef void fp();
@ -2378,7 +2409,7 @@ fp* tests_eor[] = { test_EOR_IMM, test_EOR_ZP, test_EOR_ZPX, test_EOR_ABS, test_
fp* tests_sta[] = { test_STA_ZP, test_STA_ZPX, test_STA_ABS, test_STA_ABSX, test_STA_ABSY, test_STA_INDX, test_STA_INDY };
fp* tests_pha_pla[] = { test_PHA, test_PLA, test_PLA_N, test_PLA_Z, test_PHA_PLA };
fp* tests_txs_tsx[] = { test_TXS, test_TSX, test_TXS_Z };
fp* tests_php_plp[] = { test_PHP, test_PLP_no_flags, test_PLP, test_PLP2 };
fp* tests_php_plp[] = { test_PHP, test_PHP_no_flags, test_PLP, test_PLP2 };
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_multiple };
@ -2387,6 +2418,7 @@ fp* tests_bit[] = { test_BIT_multiple };
fp* tests_jsr_rts[] = { test_JSR, test_JSR_RTS, test_RTS };
fp* tests_brk[] = { test_BRK };
fp* tests_branch[] = { test_branching_multiple };
fp* tests_rti[] = { test_RTI };
#define RUN(suite) run_suite(suite, sizeof(suite)/sizeof(fp*))
@ -2399,6 +2431,7 @@ void run_suite(fp * *suite, int size) {
}
void run_tests() {
RUN(tests_rti);
RUN(tests_branch);
RUN(tests_sbc);
RUN(tests_brk);