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Add disassembler, for reference.
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Lawrence Kesteloot
parent
cd7dd66e5e
commit
e82162163a
128
d6502.c
Normal file
128
d6502.c
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/* d6502 v 0.1 */
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#include <stdio.h>
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#include <stdlib.h>
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int main(int argc, char **argv) {
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FILE *file;
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char *buffer;
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unsigned long fileLen;
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int address;
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int i;
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int currentbyte;
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int previousbyte;
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int paramcount;
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int addrmode;
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char *opcode;
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char *pad;
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char *pre;
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char *post;
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// Padding for 1,2 & 3 byte instructions
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char *padding[3] = {" "," ",""};
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// 57 Instructions + Undefined ("???")
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char *instruction[58] = {
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// 0 1 2 3 4 5 6 7 8 9
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"ADC","AND","ASL","BCC","BCS","BEQ","BIT","BMI","BNE","BPL", // 0
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"BRK","BVC","BVS","CLC","CLD","CLI","CLV","CMP","CPX","CPY", // 1
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"DEC","DEX","DEY","EOR","INC","INX","INY","JMP","JSR","LDA", // 2
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"LDX","LDY","LSR","NOP","ORA","PHA","PHP","PLA","PLP","ROL", // 3
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"ROR","ROT","RTI","RTS","SBC","SEC","SED","SEI","STA","STX", // 4
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"STY","TAX","TAY","TSX","TXA","TXS","TYA","???"}; // 5
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// This is a lookup of the text formating required for mode output, plus one entry to distinguish relative mode
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char *modes[9][2]={{"",""},{"#",""},{"",",X"},{"",",Y"},{"(",",X)"},{"(","),Y"},{"(",")"},{"A",""},{"",""}};
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// Opcode Properties for 256 opcodes {length_in_bytes, mnemonic_lookup, mode_chars_lookup}
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int opcode_props[256][3] = {
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// 0 1 2 3 4 5 6 7 8 9 A B C D E F
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// ******** -------- ******** -------- ******** -------- ******** -------- ******** -------- ******** -------- ******** -------- ******** --------
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{1,10,0},{2,34,4},{1,57,0},{1,57,0},{1,57,0},{2,34,0},{2,2,0}, {1,57,0},{1,36,0},{2,34,1},{1,2,7}, {1,57,0},{1,57,0},{3,34,0},{3,2,0}, {1,57,0}, // 0
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{2,9,8}, {2,34,5},{1,57,0},{1,57,0},{1,57,0},{2,34,2},{2,2,2}, {1,57,0},{1,13,0},{3,34,3},{1,57,0},{1,57,0},{1,57,0},{3,34,2},{3,2,2}, {1,57,0}, // 1
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{3,28,0},{2,1,4}, {1,57,0},{1,57,0},{2,6,0}, {2,1,0}, {2,39,0},{1,57,0},{1,38,0},{2,1,1}, {1,39,7},{1,57,0},{3,6,0}, {3,1,0}, {3,39,0},{1,57,0}, // 2
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{2,7,8}, {2,1,5}, {1,57,0},{1,57,0},{1,57,0},{2,1,2}, {2,39,2},{1,57,0},{1,45,0},{3,1,3}, {1,57,0},{1,57,0},{1,57,0},{3,1,2}, {3,39,2},{1,57,0}, // 3
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{1,42,0},{2,23,4},{1,57,0},{1,57,0},{1,57,0},{2,23,0},{2,32,0},{1,57,0},{1,35,0},{2,23,1},{1,32,7},{1,57,0},{3,27,0},{3,23,0},{3,32,0},{1,57,0}, // 4
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{2,11,8},{2,23,5},{1,57,0},{1,57,0},{1,57,0},{2,23,2},{2,32,2},{1,57,0},{1,15,0},{3,23,3},{1,57,0},{1,57,0},{1,57,0},{3,23,2},{3,32,2},{1,57,0}, // 5
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{1,43,0},{2,0,4}, {1,57,0},{1,57,0},{1,57,0},{2,0,0}, {2,40,0},{1,57,0},{1,37,0},{2,0,1}, {1,41,7},{1,57,0},{3,27,6},{3,0,0}, {3,40,0},{1,57,0}, // 6
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{2,12,8},{2,0,5}, {1,57,0},{1,57,0},{1,57,0},{2,0,2}, {2,40,2},{1,57,0},{1,47,0},{3,0,3}, {1,57,0},{1,57,0},{1,57,0},{3,0,2}, {3,40,2},{1,57,0}, // 7
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{1,57,0},{2,48,4},{1,57,0},{1,57,0},{2,50,0},{2,48,0},{2,49,0},{1,57,0},{1,22,0},{1,57,0},{1,54,0},{1,57,0},{3,50,0},{3,48,0},{3,49,0},{1,57,0}, // 8
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{2,3,8}, {2,48,5},{1,57,0},{1,57,0},{2,50,2},{2,48,2},{2,49,3},{1,57,0},{1,56,0},{3,48,3},{1,55,0},{1,57,0},{1,57,0},{3,48,2},{1,57,0},{1,57,0}, // 9
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{2,31,1},{2,29,4},{2,30,1},{1,57,0},{2,31,0},{2,29,0},{2,30,0},{1,57,0},{1,52,0},{2,29,1},{1,51,0},{1,57,0},{3,31,0},{3,29,0},{3,30,0},{1,57,0}, // A
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{2,4,8}, {2,29,5},{1,57,0},{1,57,0},{2,31,2},{2,29,2},{2,30,3},{1,57,0},{1,16,0},{3,29,3},{1,53,0},{1,57,0},{3,31,2},{3,29,2},{3,30,3},{1,57,0}, // B
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{2,19,1},{2,17,4},{1,57,0},{1,57,0},{2,19,0},{2,17,0},{2,20,0},{1,57,0},{1,26,0},{2,17,1},{1,21,0},{1,57,0},{3,19,0},{3,17,0},{3,20,0},{1,57,0}, // C
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{2,8,8}, {2,17,5},{1,57,0},{1,57,0},{1,57,0},{2,17,2},{2,20,2},{1,57,0},{1,14,0},{3,17,3},{1,57,0},{1,57,0},{1,57,0},{3,17,2},{3,20,2},{1,57,0}, // D
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{2,18,1},{2,44,4},{1,57,0},{1,57,0},{2,18,0},{2,44,0},{2,24,0},{1,57,0},{1,25,0},{2,44,1},{1,33,0},{1,57,0},{3,18,0},{3,44,0},{3,24,0},{1,57,0}, // E
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{2,5,8}, {2,44,5},{1,57,0},{1,57,0},{1,57,0},{2,44,2},{2,24,2},{1,57,0},{1,46,0},{3,44,3},{1,57,0},{1,57,0},{1,57,0},{3,44,2},{3,24,2},{1,57,0} // F
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};
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if (argc < 2) { //If no parameters given, display usage instructions and exit.
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fprintf(stderr, "Usage: %s filename address\n\n", argv[0]);
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fprintf(stderr, "Example: %s dump.rom E000\n", argv[0]);
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exit(1);
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}
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if (argc == 3) {
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address = strtol(argv[2], NULL, 16); //If second parameter, accept it as HEX address for start of dissasembly.
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}
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file = fopen(argv[1], "rb"); //Open file
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if (!file) {
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fprintf(stderr, "Can't open file %s", argv[1]); //Error if file not found
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exit(1);
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}
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fseek(file, 0, SEEK_END); //Seek to end of file to find length
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fileLen = ftell(file);
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fseek(file, 0, SEEK_SET); //And back to the start
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buffer = (char * ) malloc(fileLen + 1); //Set up file buffer
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if (!buffer) { //If memory allocation error...
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fprintf(stderr, "Memory allocation error!"); //...display message...
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fclose(file); //...and close file
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exit(1);
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}
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fread(buffer, fileLen, 1, file); //Read entire file into buffer and...
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fclose(file); //...close file
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paramcount = 0;
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printf(" * = %04X \n", address); //Display org address
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for (i = 0; i < fileLen; ++i) { //Start proccessing loop.
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previousbyte = currentbyte;
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currentbyte = ((unsigned char * ) buffer)[i];
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if (paramcount == 0) {
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printf("%04X ", address); //Display current address at beginning of line
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paramcount = opcode_props[currentbyte][0]; //Get instruction length
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opcode = instruction[opcode_props[currentbyte][1]]; //Get opcode name
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addrmode = opcode_props[currentbyte][2]; //Get info required to display addressing mode
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pre = modes[addrmode][0]; //Look up pre-operand formatting text
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post = modes[addrmode][1]; //Look up post-operand formatting text
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pad = padding[(paramcount - 1)]; //Calculate correct padding for output alignment
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address = address + paramcount; //Increment address
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}
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if (paramcount != 0) //Keep track of possition within instruction
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paramcount = paramcount - 1;
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printf("%02X ", currentbyte); //Display the current byte in HEX
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if (paramcount == 0) {
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printf(" %s %s %s", pad, opcode, pre); //Pad text, display instruction name and pre-operand chars
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if (pad == " ") { //Check if single operand instruction
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if (addrmode != 8) { //If not using relative addressing ...
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printf("$%02X", currentbyte); //...display operand
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} else { //Addressing mode is relative...
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printf("$%02X", (address + ((currentbyte < 128) ? currentbyte : currentbyte - 256))); //...display relative address.
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}
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}
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if (pad == "") //Check if two operand instruction and if so...
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printf("$%02X%02X", currentbyte, previousbyte); //...display operand
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printf("%s\n", post); //Display post-operand chars
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}
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}
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printf("%02X .END\n", address); //Add .END directive to end of output
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free(buffer); //Return buffer memory to the system
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return 0; //All done, exit to the OS
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}
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