fixed PHP flag handling + test

cpu.c

@@ -31,8 +31,17 @@ void set_NZ_flags(State6502 * state, byte value) {
 }
 
 byte flags_as_byte(State6502 * state) {
-	byte flags_value;
-	memcpy(&flags_value, &state->flags, sizeof(Flags));
+	byte flags_value = 0;
+	flags_value |= state->flags.c << 0;
+	flags_value |= state->flags.z << 1;
+	flags_value |= state->flags.i << 2;
+	flags_value |= state->flags.d << 3;
+	//flag B is active with PHP
+	flags_value |= 1 << 4;
+	//unused bit is active with PHP
+	flags_value |= 1 << 5;
+	flags_value |= state->flags.v << 6;
+	flags_value |= state->flags.n << 7;
 	return flags_value;
 }
 
@@ -350,8 +359,7 @@ void PLP_(State6502* state) {
 }
 
 void PHP_(State6502 * state) {
-	byte flags_value;
-	memcpy(&flags_value, &state->flags, sizeof(Flags));
+	byte flags_value = flags_as_byte(state);
 	push_byte_to_stack(state, flags_value);
 }
 

emu6502.c

@@ -22,12 +22,18 @@ byte* read_nestest() {
 		int err = errno;
 		exit(1);
 	}
-	byte buffer[NESTEST_SIZE];
+	static byte buffer[NESTEST_SIZE];
 	int read = fread(&buffer, sizeof(byte), NESTEST_SIZE, file);
 	fclose(file);
 	return buffer;
 }
 
+byte debug_flags_as_byte(State6502* state) {
+	byte flags_value = 0;
+	memcpy(&flags_value, &state->flags, sizeof(Flags));
+	return flags_value;
+}
+
 void run_nestest() {
 	State6502 state;
 	clear_state(&state);
@@ -38,16 +44,19 @@ void run_nestest() {
 	memcpy(state.memory + NESTEST_DST, bin, NESTEST_SIZE);
 	memcpy(state.memory + 0x8000, bin, NESTEST_SIZE);
 	state.pc = NESTEST_DST;
+	//a little cheat to simulate probably a JSR and SEI at the beginning 
+	state.sp = 0xfd;
+	state.flags.i = 1;
 	do{
 		char* dasm = disassemble_6502_to_string(state.memory, state.pc);
-		printf("%-50s  A:%02X X:%02X Y:%02X P:%02X SP:%02X\n", dasm, state.a, state.x, state.y, flags_as_byte(&state), state.sp);
+		printf("%-50s  A:%02X X:%02X Y:%02X P:%02X SP:%02X\n", dasm, state.a, state.x, state.y, debug_flags_as_byte(&state), state.sp);
 		emulate_6502_op(&state);
 	} while (state.flags.b != 1);
 }
 
 int main()
 {
-	//run_nestest();
-	run_tests();
+	run_nestest();
+	//run_tests();
 	return 0;
 }

flags.h

@@ -4,12 +4,12 @@
 
 typedef struct Flags {
 	//flags high to low: NV-BDIZC
-	uint8_t c : 1;  //set if last operation caused an overflow from bit 7 of the result or an underflow from bit 0
-	uint8_t z : 1; //set if the result of the last operation was zero
-	uint8_t i : 1; //set with SEI and cleared with CLI
-	uint8_t d : 1; //set with SEC and cleared with CLD
-	uint8_t b : 1; //set when BRK executed
-	uint8_t pad : 1; //not used
-	uint8_t v : 1; //if the result has yielded an invalid two's complement result
-	uint8_t n : 1; //set if the result of the last operation set bit 7 to one
+	uint8_t c : 1;  //0 - set if last operation caused an overflow from bit 7 of the result or an underflow from bit 0
+	uint8_t z : 1; //1 - set if the result of the last operation was zero
+	uint8_t i : 1; //2 - set with SEI and cleared with CLI
+	uint8_t d : 1; //3 - set with SEC and cleared with CLD
+	uint8_t b : 1; //4 - set when BRK executed
+	uint8_t pad : 1; //5 - not used
+	uint8_t v : 1; //6 - if the result has yielded an invalid two's complement result
+	uint8_t n : 1; //7 - set if the result of the last operation set bit 7 to one
 } Flags;

test6502.c

@@ -2001,7 +2001,6 @@ void test_PHP() {
 	state.flags.d = 1;
 	state.flags.i = 1;
 	state.flags.v = 1;
-	state.sp = 0xFF;
 
 	//arrange
 	char program[] = { PHP };
@@ -2018,6 +2017,27 @@ void test_PHP() {
 	test_cleanup(&state);
 }
 
+void test_PLP_no_flags() {
+	//initialize
+	State6502 state = create_blank_state();
+	//no flags are set
+
+	//arrange
+	char program[] = { PHP };
+	memcpy(state.memory, program, sizeof(program));
+
+	//act
+	test_step(&state);
+
+	//assert	
+	assert_sp(&state, 0xFE);
+	byte expected_value = (1 << 4) | (1 << 5);
+	assert_memory(&state, 0x1FF, expected_value);
+
+	//cleanup
+	test_cleanup(&state);
+}
+
 void test_PLP() {
 	State6502 state = create_blank_state();
 	state.sp = 0xFE;
@@ -2051,7 +2071,7 @@ void test_PLP2() {
 	//arrange
 	char program[] = { PLP };
 	memcpy(state.memory, program, sizeof(program));
-	state.memory[0x1FF] = 0x04; //all flags should be on
+	state.memory[0x1FF] = 0x04; //only flag i should be set
 
 	//act
 	test_step(&state);
@@ -2494,7 +2514,7 @@ 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, test_PLP2 };
+fp* tests_php_plp[] = { test_PHP, test_PLP_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 };