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implemented ROR

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This commit is contained in:
jborza 2019-04-20 08:49:28 +02:00
parent a4a56ddc9f
commit a11d260f98
1 changed files with 31 additions and 21 deletions
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52
cpu.c
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@ -14,6 +14,10 @@ int is_negative(byte value) {
return ((1 << 7) & value) != 0;
}
void set_z_flag(State6502* state, byte value) {
state->flags.z = value == 0;
}
void set_NV_flags(State6502 * state, byte value) {
//N flag
state->flags.n = is_negative(value);
@ -21,13 +25,7 @@ void set_NV_flags(State6502 * state, byte value) {
}
void set_NZ_flags(State6502 * state, byte value) {
//Z flag
if (value) {
state->flags.z = 0;
}
else {
state->flags.z = 1;
}
set_z_flag(state, value);
//N flag
state->flags.n = is_negative(value);
}
@ -167,7 +165,7 @@ void CPY(State6502 * state, byte operand) {
byte asl(State6502* state, byte operand) {
byte result = operand << 1;
state->flags.c = operand > 0x80;
set_NV_flags(state, result);
set_NZ_flags(state, result);
return result;
}
@ -184,7 +182,7 @@ void ASL_MEM(State6502* state, word address) {
byte lsr(State6502* state, byte operand) {
byte result = operand >> 1;
state->flags.c = (operand & 0x01) != 0;
set_NV_flags(state, result);
set_NZ_flags(state, result);
return result;
}
@ -197,15 +195,11 @@ void LSR_MEM(State6502* state, word address) {
state->memory[address] = lsr(state, operand);
}
byte ror(State6502* state, byte operand) {
//TODO implement
}
byte rol(State6502* state, byte operand) {
word result_word = (operand << 1) | state->flags.c;
state->flags.c = result_word > 0xFF;
byte result = result_word & 0xFF;
set_NV_flags(state, result);
set_NZ_flags(state, result);
return result;
}
@ -218,6 +212,23 @@ void ROL_MEM(State6502* state, word address) {
state->memory[address] = rol(state, operand);
}
byte ror(State6502* state, byte operand) {
word result_word = (operand >> 1) | (state->flags.c << 7);
state->flags.c = (result_word & 0x01) != 0;
byte result = result_word & 0xFF;
set_NZ_flags(state, result);
return result;
}
void ROR_A(State6502 * state) {
state->a = rol(state, state->a);
}
void ROR_MEM(State6502 * state, word address) {
byte operand = state->memory[address];
state->memory[address] = ror(state, operand);
}
word pop_word(State6502 * state) {
byte low = pop_byte(state);
byte high = pop_byte(state);
@ -469,11 +480,11 @@ int emulate_6502_op(State6502 * state) {
case ROL_ZPX: ROL_MEM(state, get_address_zero_page_x(state)); break;
case ROL_ABS: ROL_MEM(state, get_address_absolute(state)); break;
case ROL_ABSX: ROL_MEM(state, get_address_absolute_x(state)); break;
case ROR_ACC: unimplemented_instruction(state); break;
case ROR_ZP: unimplemented_instruction(state); break;
case ROR_ZPX: unimplemented_instruction(state); break;
case ROR_ABS: unimplemented_instruction(state); break;
case ROR_ABSX: unimplemented_instruction(state); break;
case ROR_ACC: ROR_A(state); break;
case ROR_ZP: ROR_MEM(state, get_address_zero_page(state)); break;
case ROR_ZPX: ROR_MEM(state, get_address_zero_page_x(state)); break;
case ROR_ABS: ROR_MEM(state, get_address_absolute(state)); break;
case ROR_ABSX: ROR_MEM(state, get_address_absolute_x(state)); break;
case SBC_IMM: SBC(state, pop_byte(state)); break;
case SBC_ZP: SBC(state, get_byte_zero_page(state)); break;
case SBC_ZPX: SBC(state, get_byte_zero_page_x(state)); break;
@ -500,5 +511,4 @@ int emulate_6502_op(State6502 * state) {
unimplemented_instruction(state); break;
}
return 0;
}
}