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cleaning decode source code

This commit is contained in:
Thiago Auler 2017-11-12 22:27:51 -02:00
parent d942e682ae
commit 10f9063872
4 changed files with 64 additions and 248 deletions
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BIN
doc/6502 opcodes tables.pdf Normal file
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88
src/6502.c
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@ -4,7 +4,8 @@
#include "inc/memory.h"
#include "inc/opcodes.h"
oc1 opcode_decoded_1;
oc2 opcode_decoded_2;
void init()
{
@ -75,6 +76,7 @@ void decode()
{
opcode_decoded_1 = XXX;
opcode_decoded_2 = XXX;
addressing_mode = XXX;
}
if (ir == 0x04 || ir == 0x0C || ir == 0x14 || ir == 0x1A || ir == 0x1C || ir == 0x34 || ir == 0x3A ||
@ -84,82 +86,12 @@ void decode()
{
opcode_decoded_1 = XXX;
opcode_decoded_2 = XXX;
addressing_mode = XXX;
}
}
void execute()
{
/*switch (opcode_decoded_2)
{
case JSR:
printf("abs ");
pc++;
pc++;
break;
case BPL: case BMI: case BVC: case BVS:
case BCC: case BCS: case BNE: case BEQ:
printf("rel ");
pc++;
break;
case TXA: case TXS: case TAX: case TSX: case DEX:
case NOP: case CLC: case SEC: case CLI: case SEI:
case TYA: case CLV: case CLD: case SED: case PHP:
case PLP: case PHA: case PLA: case DEY: case TAY:
case INY: case INX: case BRK: case RTI: case RTS:
printf("imp ");
break;
default:
switch (addressing_mode)
{
case immediate:
printf("imm ");
pc++;
break;
case zero_page:
printf("zpg ");
pc++;
break;
case accumulator:
printf("acc ");
break;
case absolute:
printf("abs ");
pc++;
pc++;
break;
case indirect_y:
printf("iny ");
pc++;
break;
case zero_page_x:
printf("zpx ");
pc++;
break;
case absolute_y:
printf("aby ");
pc++;
pc++;
break;
case absolute_x:
printf("abx ");
pc++;
pc++;
break;
case indirect_x:
printf("inx ");
pc++;
break;
case zero_page_y:
printf("zpy ");
pc++;
break;
default:
break;
}
break;
}*/
switch (opcode_decoded_2)
{
case BRK:
@ -289,15 +221,11 @@ void execute()
void run()
{
//while (pc != 0)
while (pc != 0)
{
//fetch();
for (int i = 0x00; i <= 0xFF; i++)
{
ir = i;
decode();
execute();
}
fetch();
decode();
execute();
}
}

2
src/inc/opcodes.h
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@ -99,8 +99,6 @@ typedef enum opcodes oc1;
typedef enum opcodes_comp oc2;
typedef enum address_mode am;
oc1 opcode_decoded_1;
oc2 opcode_decoded_2;
am addressing_mode;
void xxx(); // invalid opcode

222
src/opcodes.c
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@ -1,465 +1,355 @@
#include <stdio.h>
#include "inc/opcodes.h"
#include "inc/memory.h"
int zz = 0;
void decode_addressing_mode()
db fetch_operand(dw address)
{
switch (opcode_decoded_2)
mem.mar = address;
mem_read();
return mem.mdr;
}
dw fetch_address()
{
dw word;
db low_byte;
db high_byte;
low_byte = fetch_operand(pc);
pc = pc + 1;
high_byte = fetch_operand(pc);
pc = pc + 1;
word = high_byte << 8; // shifts high byte to its place
word = word | low_byte; // appends low byte to form the complete word
return word;
}
db decode_operand()
{
db operand;
db byte;
dw word;
switch (addressing_mode)
{
case XXX:
printf("/---] ");
case immediate:
operand = fetch_operand(pc);
pc = pc + 1;
break;
case JSR:
printf("/abs] ");
case zero_page:
byte = fetch_operand(pc);
word = 0x0000 | byte;
operand = fetch_operand(word);
pc = pc + 1;
break;
case BPL: case BMI: case BVC: case BVS:
case BCC: case BCS: case BNE: case BEQ:
printf("/rel] ");
case zero_page_x:
byte = fetch_operand(pc);
word = 0x0000 | byte;
word = word + x;
operand = fetch_operand(word);
pc = pc + 1;
break;
case TXA: case TXS: case TAX: case TSX: case DEX:
case NOP: case CLC: case SEC: case CLI: case SEI:
case TYA: case CLV: case CLD: case SED: case PHP:
case PLP: case PHA: case PLA: case DEY: case TAY:
case INY: case INX: case BRK: case RTI: case RTS:
printf("/imp] ");
case zero_page_y:
byte = fetch_operand(pc);
word = 0x0000 | byte;
word = word + y;
operand = fetch_operand(word);
pc = pc + 1;
break;
default:
switch (addressing_mode)
{
case immediate:
printf("/imm] ");
break;
case zero_page:
printf("/zpg] ");
break;
case accumulator:
printf("/acc] ");
break;
case absolute:
printf("/abs] ");
break;
case indirect_y:
printf("/iny] ");
break;
case zero_page_x:
printf("/zpx] ");
break;
case absolute_y:
printf("/aby] ");
break;
case absolute_x:
printf("/abx] ");
break;
case indirect_x:
printf("/inx] ");
break;
case zero_page_y:
printf("/zpy] ");
break;
}
case accumulator:
operand = ac;
break;
}
if (++zz % 8 == 0) { printf("\n"); }
return operand;
}
void xxx()
{
// invalid opcode
printf("%02X:[---", ir);
decode_addressing_mode();
return nop();
}
void adc()
{
// add memory to accumalator with carry
printf("%02X:[ADC", ir);
decode_addressing_mode();
}
void and()
{
// and memory with accumulator
printf("%02X:[AND", ir);
decode_addressing_mode();
}
void asl()
{
// shift left one bit (memory on accumulator)
printf("%02X:[ASL", ir);
decode_addressing_mode();
}
void bcc()
{
// branch on carry clear
printf("%02X:[BCC", ir);
decode_addressing_mode();
}
void bcs()
{
// branch on carry set
printf("%02X:[BSC", ir);
decode_addressing_mode();
}
void beq()
{
// branch on result zero
printf("%02X:[BEQ", ir);
decode_addressing_mode();
}
void bit()
{
// test bits in memory with accumulator
printf("%02X:[BIT", ir);
decode_addressing_mode();
}
void bmi()
{
// branch on result minus
printf("%02X:[BMI", ir);
decode_addressing_mode();
}
void bne()
{
// branch on result not zero
printf("%02X:[BNE", ir);
decode_addressing_mode();
}
void bpl()
{
// branch on result plus
printf("%02X:[BPL", ir);
decode_addressing_mode();
}
void brk()
{
// force break
printf("%02X:[BRK", ir);
decode_addressing_mode();
}
void bvc()
{
// branch on overflow clear
printf("%02X:[BVC", ir);
decode_addressing_mode();
}
void bvs()
{
// branch on overflow set
printf("%02X:[BVS", ir);
decode_addressing_mode();
}
void clc()
{
// clear carry flag
printf("%02X:[CLC", ir);
decode_addressing_mode();
}
void cld()
{
// clear decimal mode
printf("%02X:[CLD", ir);
decode_addressing_mode();
}
void cli()
{
// clear interrupt disable bit
printf("%02X:[CLI", ir);
decode_addressing_mode();
}
void clv()
{
// clear overflow flag
printf("%02X:[CLV", ir);
decode_addressing_mode();
}
void cmp()
{
// compare memory with accumulator
printf("%02X:[CMP", ir);
decode_addressing_mode();
}
void cpx()
{
// compare memory and index x
printf("%02X:[CPX", ir);
decode_addressing_mode();
}
void cpy()
{
// compare memory and index y
printf("%02X:[CPY", ir);
decode_addressing_mode();
}
void dec()
{
// decrement memory by one
printf("%02X:[DEC", ir);
decode_addressing_mode();
}
void dex()
{
// decrement index x by one
printf("%02X:[DEX", ir);
decode_addressing_mode();
}
void dey()
{
// decrement index y by one
printf("%02X:[DEY", ir);
decode_addressing_mode();
}
void eor()
{
// exclusive-or memory with accumulator
printf("%02X:[EOR", ir);
decode_addressing_mode();
}
void inc()
{
// increment memory by one
printf("%02X:[INC", ir);
decode_addressing_mode();
}
void inx()
{
// increment index x by one
printf("%02X:[INX", ir);
decode_addressing_mode();
}
void iny()
{
// increment index y by one
printf("%02X:[INY", ir);
decode_addressing_mode();
}
void jmp()
{
// jump to new location
printf("%02X:[JMP", ir);
decode_addressing_mode();
}
void jsr()
{
// jump to new location saving return address
printf("%02X:[JSR", ir);
decode_addressing_mode();
}
void lda()
{
// load accumulator with memory
printf("%02X:[LDA", ir);
decode_addressing_mode();
}
void ldx()
{
// load index x with memory
printf("%02X:[LDX", ir);
decode_addressing_mode();
}
void ldy()
{
// load index y with memory
printf("%02X:[LDY", ir);
decode_addressing_mode();
}
void lsr()
{
// shift one bit right (memory or accumulator)
printf("%02X:[LSR", ir);
decode_addressing_mode();
}
void nop()
{
// no operation
printf("%02X:[NOP", ir);
decode_addressing_mode();
}
void ora()
{
// or memory with accumulator
printf("%02X:[ORA", ir);
decode_addressing_mode();
}
void pha()
{
// push accumulator on stack
printf("%02X:[PHA", ir);
decode_addressing_mode();
}
void php()
{
// push processor status on stack
printf("%02X:[PHP", ir);
decode_addressing_mode();
}
void pla()
{
// pull accumulator from stack
printf("%02X:[PLA", ir);
decode_addressing_mode();
}
void plp()
{
// pull processor status from stack
printf("%02X:[PLP", ir);
decode_addressing_mode();
}
void rol()
{
// rotate on bit left (memory or accumulator)
printf("%02X:[ROL", ir);
decode_addressing_mode();
}
void ror()
{
// rotate on bit right (memory or accumulator)
printf("%02X:[ROR", ir);
decode_addressing_mode();
}
void rti()
{
// return from interrupt
printf("%02X:[RTI", ir);
decode_addressing_mode();
}
void rts()
{
// retrun from subroutine
printf("%02X:[RTS", ir);
decode_addressing_mode();
}
void sbc()
{
// subtract memory from accumulator with borrow
printf("%02X:[SBC", ir);
decode_addressing_mode();
}
void sec()
{
// set carry flag
printf("%02X:[SEC", ir);
decode_addressing_mode();
}
void sed()
{
// set decimal flag
printf("%02X:[SED", ir);
decode_addressing_mode();
}
void sei()
{
// set interrupt disable status
printf("%02X:[SEI", ir);
decode_addressing_mode();
}
void sta()
{
// store accumulator in memory
printf("%02X:[STA", ir);
decode_addressing_mode();
}
void stx()
{
// store index x in memory
printf("%02X:[STX", ir);
decode_addressing_mode();
}
void sty()
{
// store index y in memory
printf("%02X:[STY", ir);
decode_addressing_mode();
}
void tax()
{
// transfer accumulator to index x
printf("%02X:[TAX", ir);
decode_addressing_mode();
}
void tay()
{
// transfer accumulator to index y
printf("%02X:[TAY", ir);
decode_addressing_mode();
}
void tsx()
{
// transfer stack pointer to index x
printf("%02X:[TSX", ir);
decode_addressing_mode();
}
void txa()
{
// transfer index x to accumulator
printf("%02X:[TXA", ir);
decode_addressing_mode();
}
void txs()
{
// transfer index x to stack pointer
printf("%02X:[TXS", ir);
decode_addressing_mode();
}
void tya()
{
// transfer index y to accumulator
printf("%02X:[TYA", ir);
decode_addressing_mode();
}