6502
/
dcc6502
mirror of https://github.com/tcarmelveilleux/dcc6502.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Disassemble 6501 instructions 

This adds support for the RMB, SMB bit manipulation instructions,
and the conditional jump instructions BBR and BBS which use a
new addressing mode: (zeropage, relative offset).
This commit is contained in:
Martin Vilcans 2023-03-17 16:41:29 +01:00
parent 680c212992
commit 8c69479f8c
1 changed files with 64 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
dcc6502.c
View File

@ -32,13 +32,13 @@
#include <errno.h>
#define VERSION_INFO "v2.1"
#define NUMBER_OPCODES 151
#define NUMBER_OPCODES 183
/* Exceptions for cycle counting */
#define CYCLES_CROSS_PAGE_ADDS_ONE (1 << 0)
#define CYCLES_BRANCH_TAKEN_ADDS_ONE (1 << 1)
/* The 6502's 13 addressing modes */
/* The 6502's 13 addressing modes + 1 extra for the 6501 */
typedef enum {
IMMED = 0, /* Immediate */
ABSOL, /* Absolute */
@ -52,7 +52,8 @@ typedef enum {
INDIN, /* Indexed indirect (with X) */
ININD, /* Indirect indexed (with Y) */
RELAT, /* Relative */
ACCUM /* Accumulator */
ACCUM, /* Accumulator */
ZEROP_RELAT, /* Zeropage, relative (6501 conditional jumps) */
} addressing_mode_e;
/** Some compilers don't have EOK in errno.h */
@ -131,6 +132,42 @@ static opcode_t g_opcode_table[NUMBER_OPCODES] = {
{0x58, "CLI", IMPLI, 2, 0}, /* CLI */
{0x07, "RMB0", ZEROP, 5, 0}, /* RMB0 */
{0x17, "RMB1", ZEROP, 5, 0}, /* RMB1 */
{0x27, "RMB2", ZEROP, 5, 0}, /* RMB2 */
{0x37, "RMB3", ZEROP, 5, 0}, /* RMB3 */
{0x47, "RMB4", ZEROP, 5, 0}, /* RMB4 */
{0x57, "RMB5", ZEROP, 5, 0}, /* RMB5 */
{0x67, "RMB6", ZEROP, 5, 0}, /* RMB6 */
{0x77, "RMB7", ZEROP, 5, 0}, /* RMB7 */
{0x87, "SMB0", ZEROP, 5, 0}, /* SMB0 */
{0x97, "SMB1", ZEROP, 5, 0}, /* SMB1 */
{0xA7, "SMB2", ZEROP, 5, 0}, /* SMB2 */
{0xB7, "SMB3", ZEROP, 5, 0}, /* SMB3 */
{0xC7, "SMB4", ZEROP, 5, 0}, /* SMB4 */
{0xD7, "SMB5", ZEROP, 5, 0}, /* SMB5 */
{0xE7, "SMB6", ZEROP, 5, 0}, /* SMB6 */
{0xF7, "SMB7", ZEROP, 5, 0}, /* SMB7 */
{0x0F, "BBR0", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR0 */
{0x1F, "BBR1", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR1 */
{0x2F, "BBR2", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR2 */
{0x3F, "BBR3", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR3 */
{0x4F, "BBR4", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR4 */
{0x5F, "BBR5", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR5 */
{0x6F, "BBR6", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR6 */
{0x7F, "BBR7", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBR7 */
{0x8F, "BBS0", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS0 */
{0x9F, "BBS1", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS1 */
{0xAF, "BBS2", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS2 */
{0xBF, "BBS3", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS3 */
{0xCF, "BBS4", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS4 */
{0xDF, "BBS5", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS5 */
{0xEF, "BBS6", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS6 */
{0xFF, "BBS7", ZEROP_RELAT, 5, CYCLES_CROSS_PAGE_ADDS_ONE | CYCLES_BRANCH_TAKEN_ADDS_ONE}, /* BBS7 */
{0xB8, "CLV", IMPLI, 2, 0}, /* CLV */
{0xC9, "CMP", IMMED, 2, 0}, /* CMP */
@ -393,6 +430,7 @@ static void disassemble(char *output, uint8_t *buffer, options_t *options, uint1
int entry = 0;
int found = 0;
uint8_t byte_operand;
uint8_t byte_operand2;
uint16_t word_operand = 0;
uint16_t current_addr = *pc;
uint8_t opcode = buffer[current_addr];
@ -566,6 +604,29 @@ static void disassemble(char *output, uint8_t *buffer, options_t *options, uint1
sprintf(hex_dump, "$%04X> %02X %02X:", current_addr, opcode, byte_operand);
}
break;
case ZEROP_RELAT:
/* Get zero page address */
byte_operand = buffer[*pc + 1];
*pc += 1;
/* Get relative modifier */
byte_operand2 = buffer[*pc + 1];
*pc += 1;
// Compute displacement from first byte after full instruction.
word_operand = current_addr + 3;
if (byte_operand > 0x7Fu) {
word_operand -= ((~byte_operand2 & 0x7Fu) + 1);
} else {
word_operand += byte_operand2 & 0x7Fu;
}
sprintf(opcode_repr, "%s $%02X,$%04X", mnemonic, byte_operand, word_operand);
if (options->hex_output) {
sprintf(hex_dump, "$%04X> %02X %02X %02X:", current_addr, opcode, byte_operand, byte_operand2);
}
break;
case ACCUM:
sprintf(opcode_repr, "%s A", mnemonic);