From 5ae9274ab9fcb9b663b838bce9c14b8ba87eeccf Mon Sep 17 00:00:00 2001
From: jborza <jborza@gmail.com>
Date: Wed, 1 May 2019 22:15:03 +0200
Subject: [PATCH] correct way to clear the B flag in PLP

---
 cpu.c      |  2 +-
 test6502.c | 28 +++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/cpu.c b/cpu.c
index b44672d..e7dd6d3 100644
--- a/cpu.c
+++ b/cpu.c
@@ -343,7 +343,7 @@ void PLA_(State6502* state) {
 void PLP_(State6502* state) {
 	byte value = pop_byte_from_stack(state);
 	//we don't read the BRK flag
-	value ^= 1 << 4;
+	value &= ~(1 << 4);
 	memset(&state->flags, value, sizeof(Flags));
 }
 
diff --git a/test6502.c b/test6502.c
index 5c3e33a..cf88cb0 100644
--- a/test6502.c
+++ b/test6502.c
@@ -1967,6 +1967,32 @@ void test_PLP() {
 	test_cleanup(&state);
 }
 
+void test_PLP2() {
+	State6502 state = create_blank_state();
+	state.sp = 0xfe;
+
+	//arrange
+	char program[] = { PLP };
+	memcpy(state.memory, program, sizeof(program));
+	state.memory[0x1FF] = 0x04; //all flags should be on
+
+	//act
+	test_step(&state);
+
+	//assert	
+	assert_sp(&state, 0xFF);
+	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, 0);
+	assert_flag_i(&state, 0);
+
+	//cleanup
+	test_cleanup(&state);
+}
+
 //// JMP
 
 void test_JMP() {
@@ -2365,7 +2391,7 @@ 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 };
-fp* tests_php_plp[] = { test_PHP, test_PLP };
+fp* tests_php_plp[] = { test_PHP, 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 };