From c40499b83f238de9b1a88a080261546149784586 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Thu, 3 Dec 2020 19:03:08 +0100
Subject: some more opcodes for delay 7-seg example

---
 emu/6502.c   | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 emu/6502.h   | 10 ++++++++-
 emu/memory.c |  2 +-
 3 files changed, 77 insertions(+), 3 deletions(-)

(limited to 'emu')

diff --git a/emu/6502.c b/emu/6502.c
index e39dc38..877f3f5 100644
--- a/emu/6502.c
+++ b/emu/6502.c
@@ -252,16 +252,41 @@ void cpu_6502_step( cpu_6502_t *cpu )
 			update_negative_and_sign( cpu, cpu->A );
 			break;
 		
+		case STX_ZERO:
+			operand8 = cpu_6502_read_byte( cpu, cpu->PC );
+			cpu->PC++;
+			cpu_6502_write_byte( cpu, operand8, cpu->X );
+			break;
+		
 		case STX_ABS:
 			operand16 = cpu_6502_read_word( cpu, cpu->PC );
 			cpu->PC += 2;
 			cpu_6502_write_byte( cpu, operand16, cpu->X );
 			break;
-		
+
+		case DEX_IMPL:
+			cpu->X--;
+			update_negative_and_sign( cpu, cpu->X );
+			break;
+			
 		case DEY_IMPL:
 			cpu->Y--;
 			update_negative_and_sign( cpu, cpu->Y );
 			break;
+		
+		case INY_IMPL:
+			cpu->Y++;
+			update_negative_and_sign( cpu, cpu->Y );
+			break;
+		
+		case INC_IMPL:
+			operand8 = cpu_6502_read_byte( cpu, cpu->PC );
+			cpu->PC++;
+			tmp = cpu_6502_read_byte( cpu, operand8 );
+			tmp++;
+			cpu_6502_write_byte( cpu, operand8, tmp );
+			update_negative_and_sign( cpu, tmp );
+			break;
 			
 		case ROL_ACC:
 			tmp = ( cpu->A << 1 ) | is_carry( cpu );
@@ -274,6 +299,36 @@ void cpu_6502_step( cpu_6502_t *cpu )
 			update_negative_and_sign( cpu, cpu->A );
 			break;
 		
+		case CPX_IMM:
+			operand8 = cpu_6502_read_byte( cpu, cpu->PC );
+			cpu->PC++;
+			tmp = ( cpu->X - operand8 ) & 0xFF;
+			if( cpu->X >= operand8 ) {
+				cpu->PS |= PS_C;
+			} else {
+				cpu->PS &= ~PS_C;
+			}
+			update_negative_and_sign( cpu, tmp );
+			break;
+		
+		case SBC_IMM:
+			operand8 = cpu_6502_read_byte( cpu, cpu->PC );
+			cpu->PC++;
+			tmp = cpu->A - operand8 - ( is_carry( cpu ) ? 0 : 1 );
+			update_negative_and_sign( cpu, tmp );
+			if( tmp & 0xFF00 ) {
+				cpu->PS |= PS_C;
+			} else {
+				cpu->PS &= ~PS_C;
+			}
+			if( ( ( cpu->A ^ tmp ) & 0x80 ) && ( ( cpu->A ^ operand8 ) & 0x80 ) ) {
+				cpu->PS |= PS_V;
+			} else {
+				cpu->PS &= ~PS_V;
+			}
+			cpu->A = tmp & 0xFF;
+			break;
+		
 		case BNE_REL:
 			operand8 = cpu_6502_read_byte( cpu, cpu->PC );
 			cpu->PC++;
@@ -289,6 +344,14 @@ void cpu_6502_step( cpu_6502_t *cpu )
 				cpu->PC += (int8_t)operand8;
 			}
 			break;
+
+		case BCS_REL:
+			operand8 = cpu_6502_read_byte( cpu, cpu->PC );
+			cpu->PC++;
+			if( is_carry( cpu ) ) {
+				cpu->PC += (int8_t)operand8;
+			}
+			break;
 			
 		case JMP_ABS:
 			cpu->PC = cpu_6502_read_word( cpu, cpu->PC );
@@ -308,6 +371,9 @@ void cpu_6502_step( cpu_6502_t *cpu )
 			cpu->SP = cpu->X;
 			break;
 			
+		case NOP_IMPL:
+			break;
+			
 		default:
 			fprintf( stderr, "ERROR: Illegal opcode %02X at PC %04X\n", opcode, cpu->PC );
 			exit( EXIT_FAILURE );
diff --git a/emu/6502.h b/emu/6502.h
index baefd0f..bfc8314 100644
--- a/emu/6502.h
+++ b/emu/6502.h
@@ -48,15 +48,23 @@ enum {
 	LDY_ZERO = 0xA4,
 	LDA_IMM  = 0xA9,
 	LDA_ZERO = 0xA5,
+	STX_ZERO = 0x86,
 	STX_ABS  = 0x8E,
+	DEX_IMPL = 0xCA,
 	DEY_IMPL = 0x88,
+	INY_IMPL = 0xC8,
+	INC_IMPL = 0xE6,
 	ROL_ACC  = 0x2A,
 	BNE_REL  = 0xD0,
 	BCC_REL  = 0x90,
+	BCS_REL  = 0xB0,
 	JMP_ABS  = 0x4C,
 	JSR_ABS  = 0x20,
 	RTS_IMPL = 0x60,
-	TXS_IMPL = 0x9A
+	TXS_IMPL = 0x9A,
+	CPX_IMM  = 0xE0,
+	SBC_IMM  = 0xE9,
+	NOP_IMPL = 0xEA
 };
 
 void cpu_6502_init( cpu_6502_t *cpu, bus_t *bus, bool initialize );
diff --git a/emu/memory.c b/emu/memory.c
index e879edd..620261b 100644
--- a/emu/memory.c
+++ b/emu/memory.c
@@ -54,7 +54,7 @@ void memory_write( void *obj, uint16_t addr, uint8_t data )
 {
 	memory_t *memory = (memory_t *)obj;
 
-	if( memory->type && MEMORY_ROM ) {
+	if( memory->type & MEMORY_ROM ) {
 		// ignore writes to ROM
 	} else {
 		memory->cell[addr-memory->addr] = data;
-- 
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