vin/emu_nes
1
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

improve branching cycle accuracy

Browse Source
This commit is contained in:
Vineet K 2024-07-03 20:40:57 -04:00
parent 2236e79556
commit 4fcc8d48f4
1 changed files with 23 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
cpu.c
View File

@ -1,4 +1,5 @@
#include <libgen.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
@ -151,6 +152,20 @@ opcode_mem(enum addressing_mode mode)
return val;
}
static void
branch(uint16_t addr, bool cond)
{
if (!cond)
return;
cycles++;
addr += regs.pc;
if ((regs.pc + 1) & 0xFF00 != addr & 0xFF00)
cycles++;
regs.pc = addr;
}
void
ADC(uint16_t arg)
{
@ -201,22 +216,19 @@ ASL(uint16_t mem)
void
BCC(uint16_t arg)
{
if (regs.status.carry == 0)
regs.pc += arg, cycles++;
branch(arg, regs.status.carry == 0);
}
void
BCS(uint16_t arg)
{
if (regs.status.carry == 1)
regs.pc += arg, cycles++;
branch(arg, regs.status.carry == 1);
}
void
BEQ(uint16_t arg)
{
if (regs.status.zero == 1)
regs.pc += arg, cycles++;
branch(arg, regs.status.zero == 1);
}
void
@ -232,22 +244,19 @@ BIT(uint16_t arg)
void
BMI(uint16_t arg)
{
if (regs.status.negative == 1)
regs.pc += arg, cycles++;
branch(arg, regs.status.negative == 1);
}
void
BNE(uint16_t arg)
{
if (regs.status.zero == 0)
regs.pc += arg, cycles++;
branch(arg, regs.status.zero == 0);
}
void
BPL(uint16_t arg)
{
if (regs.status.negative == 0)
regs.pc += arg, cycles++;
branch(arg, regs.status.negative == 0);
}
void
@ -263,16 +272,14 @@ BVC(uint16_t arg)
{
//regs.status.overflow = (STATUS_TO_INT() & (1 << 6)) == 0;
//if (regs.status.overflow == 0)
if ((STATUS_TO_INT() & (1 << 6)) == 0)
regs.pc += arg, cycles++;
branch(arg, (STATUS_TO_INT() & (1 << 6)) == 0);
}
void
BVS(uint16_t arg)
{
regs.status.overflow = (STATUS_TO_INT() & (1 << 6)) != 0;
if (regs.status.overflow == 1)
regs.pc += arg, cycles++;
branch(arg, regs.status.overflow == 1);
}
void