Created CPU struct to allow multiple instances of running processors at the same time

* note: this is not multithreading; it simply allows a program to step through more than one CPU in the same process

6502-emu.c

@@ -19,21 +19,21 @@ void step_delay()
 	nanosleep(&req, &rem);
 }
 
-void run_cpu(long cycle_stop, int verbose, int mem_dump, int break_pc, int fast)
+void run_cpu(CPU * cpu, long cycle_stop, int verbose, int mem_dump, int break_pc, int fast)
 {
 	long cycles = 0;
 	int cycles_per_step = (CPU_FREQ / (ONE_SECOND / STEP_DURATION));
 	
 	for (;;) {
 		for (cycles %= cycles_per_step; cycles < cycles_per_step;) {
-			if (mem_dump) save_memory(NULL);
-			cycles += step_cpu(verbose);
-			if ((cycle_stop > 0) && (total_cycles >= cycle_stop)) goto end;
+			if (mem_dump) save_memory(cpu, NULL);
+			cycles += step_cpu(cpu, verbose);
+			if ((cycle_stop > 0) && (cpu->total_cycles >= cycle_stop)) goto end;
 			step_uart();
 
-			if (break_pc >= 0 && PC == (uint16_t)break_pc) {
+			if (break_pc >= 0 && cpu->PC == (uint16_t)break_pc) {
 				fprintf(stderr, "break at %04x\n", break_pc);
-				save_memory(NULL);
+				save_memory(cpu, NULL);
 				goto end;
 			}
 		}
@@ -96,6 +96,7 @@ int main(int argc, char *argv[])
 	int verbose, interactive, mem_dump, break_pc, fast;
 	long cycles;
 	int opt;
+	CPU *cpu;
 
 	verbose = 0;
 	interactive = 0;
@@ -164,7 +165,11 @@ int main(int argc, char *argv[])
 	   usage(argv);
 	   exit(EXIT_FAILURE);
 	}
-	if (load_rom(argv[optind], load_addr) != 0) {
+
+	cpu = create_cpu();
+	init_uart(cpu);
+
+	if (load_rom(cpu, argv[optind], load_addr) != 0) {
 		printf("Error loading \"%s\".\n", argv[optind]);
 		return EXIT_FAILURE;
 	}
@@ -172,10 +177,9 @@ int main(int argc, char *argv[])
 	if (interactive) raw_stdin(); // allow individual keystrokes to be detected
 	
 	init_tables();
-	init_uart();
 	
-	reset_cpu(a, x, y, sp, sr, pc);
-	run_cpu(cycles, verbose, mem_dump, break_pc, fast);
+	reset_cpu(cpu, a, x, y, sp, sr, pc);
+	run_cpu(cpu, cycles, verbose, mem_dump, break_pc, fast);
 	
 	return EXIT_SUCCESS;
 }

6502.h

@@ -10,18 +10,6 @@
 #define RST_VEC 0xFFFC
 #define IRQ_VEC 0xFFFE
 
-uint8_t memory[1<<16];
-uint8_t A;
-uint8_t X;
-uint8_t Y;
-uint16_t PC;
-uint8_t SP; // points to first empty stack location
-uint8_t extra_cycles;
-uint64_t total_cycles;
-
-void * read_addr;
-void * write_addr;
-
 struct StatusBits{
 	bool carry:1; // bit 0
 	bool zero:1;
@@ -38,7 +26,21 @@ union StatusReg { // this means we can access the status register as a byte, or
 	uint8_t byte;
 };
 
-union StatusReg SR;
+typedef struct {
+	uint8_t memory[1<<16];
+	uint8_t A;
+	uint8_t X;
+	uint8_t Y;
+	uint16_t PC;
+	uint8_t SP; // points to first empty stack location
+	uint8_t extra_cycles;
+	uint64_t total_cycles;
+	union StatusReg SR;
+
+	void * read_addr;
+	void * write_addr;
+	int jumping; // used to check that we don't need to increment the PC after a jump
+} CPU;
 
 typedef enum {
 	ACC,
@@ -59,7 +61,7 @@ typedef enum {
 
 typedef struct {
 	char * mnemonic;
-	void (*function)();
+	void (*function)(CPU *);
 	Mode mode;
 	uint8_t cycles;
 } Instruction;
@@ -68,10 +70,12 @@ Instruction instructions[0x100];
 
 void init_tables();
 
-void reset_cpu(int _a, int _x, int _y, int _sp, int _sr, int _pc);
+void reset_cpu(CPU *cpu, int _a, int _x, int _y, int _sp, int _sr, int _pc);
 
-int load_rom(char * filename, int load_addr);
+int load_rom(CPU *cpu, char * filename, int load_addr);
 
-int step_cpu(int verbose);
+int step_cpu(CPU *cpu, int verbose);
 
-void save_memory(char * filename);
+void save_memory(CPU *cpu, char * filename);
+
+CPU * create_cpu();

6850.c

@@ -8,8 +8,8 @@
 
 int n;
 
-void init_uart() {
-	memory[DATA_ADDR] = 0;
+void init_uart(CPU *cpu) {
+	cpu->memory[DATA_ADDR] = 0;
 	
 	uart_SR.byte = 0;
 	uart_SR.bits.TDRE = 1; // we are always ready to output data
@@ -26,15 +26,15 @@ int stdin_ready() {
 	return poll(&fds, 1, 0) == 1; // timeout = 0
 }
 
-void step_uart() {
-	if (write_addr == &memory[DATA_ADDR]) {
-		putchar(memory[DATA_ADDR]);
-		if (memory[DATA_ADDR] == '\b') printf(" \b");
+void step_uart(CPU *cpu) {
+	if (cpu->write_addr == &cpu->memory[DATA_ADDR]) {
+		putchar(cpu->memory[DATA_ADDR]);
+		if (cpu->memory[DATA_ADDR] == '\b') printf(" \b");
 		fflush(stdout);
-		write_addr = NULL;
-	} else if (read_addr == &memory[DATA_ADDR]) {
+		cpu->write_addr = NULL;
+	} else if (cpu->read_addr == &cpu->memory[DATA_ADDR]) {
 		uart_SR.bits.RDRF = 0;
-		read_addr = NULL;
+		cpu->read_addr = NULL;
 	}
 	
 	/* update input register if empty */
@@ -54,6 +54,6 @@ void step_uart() {
 		}
 	}
 	
-	memory[DATA_ADDR] = incoming_char;
-	memory[CTRL_ADDR] = uart_SR.byte;
+	cpu->memory[DATA_ADDR] = incoming_char;
+	cpu->memory[CTRL_ADDR] = uart_SR.byte;
 }

Makefile

@@ -1,4 +1,4 @@
-CFLAGS = -Wall -Wpedantic -Ofast -std=gnu99
+CFLAGS = -Wall -Wpedantic -g -std=gnu99
 LDFLAGS = -Ofast
 
 OBJ := 6502-emu.o 6502.o 6850.o