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A1Emu
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Adding cassette support and improving timing

This commit is contained in:
unknown 2019-03-16 00:29:06 -07:00
parent 1fc1395805
commit 9e036f143d
3 changed files with 554 additions and 45 deletions
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411
cpu.c
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File diff suppressed because it is too large Load Diff

1
cpu.h
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@ -32,6 +32,7 @@ struct CPU_6502{
uint16_t PC_reg;
//The bits status register are all of the processor flags, but it is its own register whose value can be pushed to the stack
uint8_t P_reg;
unsigned long long int cycles;
};

187
emulate.c
View File

@ -1,18 +1,61 @@
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <conio.h>
#include <sys/time.h>
#include "cpu.h"
unsigned DEBUG_STEP = 0;
unsigned char DEBUG_STEP = 0;
uint8_t memory[0x10000];
uint32_t tape[0x100000];
uint32_t tape_index;
char str_buffer[256];
unsigned char next_tape_index;
unsigned char tape_active;
unsigned char tape_writing;
unsigned char tape_reading;
unsigned char current_tape_value;
void print_state(CPU_6502 cpu){
printf("A: %02x X:%02x Y:%02x SP:%02x P:%02x PC:%02x\n", (int) cpu.A_reg, (int) cpu.X_reg, (int) cpu.Y_reg, (int) cpu.SP_reg, (int) cpu.P_reg, (int) cpu.PC_reg);
printf("\nNext: %02x %02x %02x\n", (int) memory[cpu.PC_reg], (int) memory[cpu.PC_reg + 1], (int) memory[cpu.PC_reg + 2]);
}
void load_tape(char *file_name){
FILE *fp;
fp = fopen(file_name, "rb");
printf("Reading from tape file named \"%s\"\n", file_name);
if(fp){
fread(tape, 4, 0x100000, fp);
fclose(fp);
} else {
printf("file error\n");
}
return;
}
void store_tape(char *file_name){
FILE *fp;
printf("Storing tape to file named \"%s\"\n", file_name);
fp = fopen(file_name, "wb");
if(fp){
fwrite(tape, 4, 0x100000, fp);
fclose(fp);
} else {
printf("file error\n");
}
}
//Special read memory routine for memory-mapped I/O
uint8_t read_mem(uint16_t index){
uint8_t output;
@ -20,7 +63,19 @@ uint8_t read_mem(uint16_t index){
if(DEBUG_STEP){
printf("READ: %04x ", index);
}
output = memory[index];
if(tape_writing && index >= 0xC000 && index <= 0xC0FF){
next_tape_index = 1;
} else if(index >= 0xC081 && index <= 0xC0FF){
if(current_tape_value){
output = memory[index];
} else {
output = memory[index&0xFFFE];
}
} else {
output = memory[index];
}
if(index == 0xD010){
memory[0xD011] &= 0x7F;
} else if((index&0xFF0F) == 0xD002){
@ -59,6 +114,10 @@ int main(){
unsigned long int last_time;
unsigned long int next_time;
struct timeval current_time;
char temp_char;
unsigned char str_index;
unsigned long long int last_cycles;
unsigned char last_cycle_diff;
cpu.A_reg = 0;
cpu.X_reg = 0;
@ -66,45 +125,62 @@ int main(){
cpu.SP_reg = 0;
cpu.P_reg = 0;
cpu.PC_reg = 0xE000;
tape_writing = 0;
tape_reading = 0;
//Load Integer Basic
fp = fopen("BASIC", "rb");
if(fp){
fread(memory + 0xE000, 1, 0x2000, fp);
fread(memory + 0xE000, 1, 0x1000, fp);
} else {
printf("Warning: could not load file named \"BASIC\".\nStarting without apple 1 BASIC loaded.\nApple 1 basic can still be loaded from a cassette file into address 0xE000.\n---\n");
}
fclose(fp);
//Load Woz's ACI
fp = fopen("WOZACI", "rb");
if(fp){
fread(memory + 0xC000, 1, 0x100, fp);
} else {
printf("file error\n");
exit(1);
}
fclose(fp);
//The emulator does not support ACI at the moment
memcpy(memory + 0xC100, memory + 0xC000, 0x100);
//Load Woz's monitor
fp = fopen("WOZMON", "rb");
if(fp){
fread(memory + 0xFF00, 1, 0x100, fp);
} else {
printf("file error 3\n");
printf("file error\n");
exit(1);
}
fclose(fp);
reset_6502(&cpu, read_mem);//Reset the cpu
cpu.cycles = 0;
last_cycles = 0;
//Initialize the timing
gettimeofday(&current_time, NULL);
last_time = current_time.tv_usec + current_time.tv_sec*1000000;
last_cycle_diff = 0;
next_tape_index = 0;
while(1){
/*Limit the speed of the processor to
* a realistic 4usec per instruction
/* Limit the speed of the processor to
* a realistic 4nsec per instruction
*
* Will count cpu cycles soon to make
* better timing.
*/
do{
gettimeofday(&current_time, NULL);
next_time = current_time.tv_usec + current_time.tv_sec*1000000;
} while(next_time - last_time < 4);
last_time = last_time + 4;
if(!DEBUG_STEP){
do{
gettimeofday(&current_time, NULL);
next_time = current_time.tv_usec + current_time.tv_sec*1000000;
} while(next_time - last_time < last_cycle_diff);
last_time = last_time + last_cycle_diff;
}
//Execute the instruction
execute_6502(&cpu, read_mem, write_mem);
@ -112,13 +188,60 @@ int main(){
//Debugging I/O
if(DEBUG_STEP){
print_state(cpu);
key_hit = getchar();
if(key_hit == '|'){
memset(str_buffer, 256, 0);
fgets(str_buffer, 256, stdin);
temp_char = str_buffer[6];
str_buffer[6] = (char) 0;
if(!strcmp(str_buffer, "resume")){
DEBUG_STEP = 0;
} else if(key_hit != ' '){
memory[0xD010] = key_hit|0x80;
memory[0xD011] = 0xFF;
gettimeofday(&current_time, NULL);
last_time = current_time.tv_usec + current_time.tv_sec*1000000;
} else if(temp_char == ' ' && !strcmp(str_buffer, "tstart")){
tape_active = 1;
str_buffer[12] = (char) 0;
if(temp_char == ' ' && !strcmp(str_buffer + 7, "write")){
tape_writing = 1;
printf("WRITING TO TAPE\n");
}
str_buffer[11] = (char) 0;
if(temp_char == ' ' && !strcmp(str_buffer + 7, "read")){
tape_reading = 1;
current_tape_value = 0;
printf("READING FROM TAPE\n");
}
tape_index = 0;
} else if(temp_char == ' ' && !strcmp(str_buffer, "tstore")){
str_index = 0;
while(str_buffer[str_index] != '\n' && str_index < 255){
str_index++;
}
str_buffer[str_index] = (char) 0;
store_tape(str_buffer + 7);
}
str_buffer[6] = temp_char;
temp_char = str_buffer[5];
str_buffer[5] = (char) 0;
if(!strcmp(str_buffer, "tstop")){
tape_active = 0;
tape_writing = 0;
tape_reading = 0;
}
if(temp_char == ' ' && !strcmp(str_buffer, "tload")){
str_index = 0;
while(str_buffer[str_index] != '\n' && str_index < 255){
str_index++;
}
str_buffer[str_index] = (char) 0;
load_tape(str_buffer + 6);
}
if(str_buffer[0] != (char) 0 && str_buffer[1] == (char) 0){
memory[0xD010] = str_buffer[0]|0x80;
memory[0xD011] |= 0x80;
}
}
@ -128,10 +251,34 @@ int main(){
if(key_hit == '|'){
DEBUG_STEP = 1;
printf("\n");
} else {
memory[0xD010] = key_hit|0x80;
memory[0xD011] |= 0x80;
}
}
last_cycle_diff = cpu.cycles - last_cycles;
//Handle tape
if(tape_active && tape_reading){
while(last_cycles < cpu.cycles){
if(!tape[tape_index]){
tape_index++;
current_tape_value = !current_tape_value;
}
tape[tape_index] -= 1;
last_cycles++;
}
} else if(tape_active && tape_writing){
tape[tape_index] += cpu.cycles - last_cycles;
if(next_tape_index){
tape_index++;
next_tape_index = 0;
}
last_cycles = cpu.cycles;
} else {
last_cycles = cpu.cycles;
}
}
}