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LSR implementation

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jborza 2019-04-19 11:44:20 +02:00
parent 411d4e8241
commit 2d86c1df28
1 changed files with 22 additions and 5 deletions
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27
cpu.c
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@ -181,6 +181,23 @@ void ASL_MEM(State6502* state, word address) {
state->memory[address] = asl(state, operand);
}
byte lsr(State6502* state, byte operand) {
byte result = operand >> 1;
state->flags.c = (operand & 0x01) != 0;
set_NV_flags(state, result);
return result;
}
void LSR_A(State6502* state) {
state->a = lsr(state, state->a);
}
void LSR_MEM(State6502* state, word address) {
byte operand = state->memory[address];
state->memory[address] = operand;
state->memory[address] = lsr(state, operand);
}
word pop_word(State6502 * state) {
byte low = pop_byte(state);
byte high = pop_byte(state);
@ -414,11 +431,11 @@ int emulate_6502_op(State6502 * state) {
case LDY_ZPX: LDY(state, get_byte_zero_page_x(state)); break;
case LDY_ABS: LDY(state, get_byte_absolute(state)); break;
case LDY_ABSX: LDY(state, get_byte_absolute_x(state)); break;
case LSR_ACC: unimplemented_instruction(state); break;
case LSR_ZP: unimplemented_instruction(state); break;
case LSR_ZPX: unimplemented_instruction(state); break;
case LSR_ABS: unimplemented_instruction(state); break;
case LSR_ABSX: unimplemented_instruction(state); break;
case LSR_ACC: LSR_A(state); break;
case LSR_ZP: LSR_MEM(state, get_address_zero_page(state)); break;
case LSR_ZPX: LSR_MEM(state, get_address_zero_page_x(state)); break;
case LSR_ABS: LSR_MEM(state, get_address_absolute(state)); break;
case LSR_ABSX: LSR_MEM(state, get_address_absolute_x(state)); break;
case ORA_IMM: ORA(state, pop_byte(state)); break;
case ORA_ZP: ORA(state, get_byte_zero_page(state)); break;
case ORA_ZPX: ORA(state, get_byte_zero_page_x(state)); break;