Apple-2-Tools
/
twoapple-reboot
mirror of https://github.com/edmccard/twoapple-reboot.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

ADC/SBC speedup (NMOS) and correct behavior for invalid BCD (CMOS)

This commit is contained in:
edmccard 2012-03-19 19:26:28 -04:00
parent 8639298c51
commit e932b9b7ac
2 changed files with 35 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
src/d6502/cmos.d
View File

@ -54,9 +54,22 @@ class Cmos : Cpu
final override void dec_subWithCarry(ubyte val)
{
super.dec_subWithCarry(val);
int a = accumulator;
int al = (a & 0x0F) - (val & 0x0F) - !flag.carry;
a = a - val - !flag.carry;
if (a < 0)
a = a - 0x60;
if (al < 0)
a = a - 0x06;
uint diff = accumulator - val - !flag.carry;
flag.overflow =
((accumulator ^ diff) & 0x80) &&
((accumulator ^ val) & 0x80);
flag.carry = (diff < 0x100);
peek(programCounter);
flag.zero_ = flag.negative_ = accumulator;
flag.zero_ = flag.negative_ = accumulator = cast(ubyte)a;
}
final void addrZeropageI()

47
src/d6502/cpu.d
View File

@ -352,48 +352,41 @@ class Cpu : CpuBase
void dec_addWithCarry(ubyte val)
{
uint bcdSum = (accumulator & 0x0F) + (val & 0x0F) + flag.carry;
int a = accumulator;
int al = (a & 0x0F) + (val & 0x0F) + flag.carry;
if (al >= 0x0A)
al = ((al + 0x06) & 0x0F) + 0x10;
a = (a & 0xF0) + (val & 0xF0) + al;
if (bcdSum >= 10)
bcdSum = (bcdSum - 10) | 0x10;
bcdSum += (accumulator & 0xF0) + (val & 0xF0);
flag.negative_ = cast(ubyte)bcdSum;
flag.negative_ = flag.zero_ = cast(ubyte)a;
flag.overflow =
(!((accumulator ^ val) & 0x80)) && ((val ^ bcdSum) & 0x80);
(!((accumulator ^ val) & 0x80)) && ((val ^ a) & 0x80);
if (bcdSum > 0x9f)
bcdSum += 0x60;
if (a >= 0xA0)
a = a + 0x60;
flag.zero_ = cast(ubyte)(accumulator + val + (flag.carry ? 1 : 0));
flag.carry = (bcdSum > 0xFF);
accumulator = cast(ubyte)bcdSum;
flag.carry = (a >= 0x100);
accumulator = cast(ubyte)a;
}
void dec_subWithCarry(ubyte val)
{
uint diff = accumulator - val - (flag.carry ? 0 : 1);
int a = accumulator;
int al = (a & 0x0F) - (val & 0x0F) - !flag.carry;
if (al < 0)
al = ((al - 0x06) & 0x0F) - 0x10;
a = (a & 0xF0) - (val & 0xF0) + al;
if (a < 0)
a = a - 0x60;
uint diff = accumulator - val - !flag.carry;
flag.overflow =
((accumulator ^ diff) & 0x80) &&
((accumulator ^ val) & 0x80);
uint al = (accumulator & 0x0F) - (val & 0x0F) -
(flag.carry ? 0 : 1);
uint ah = (accumulator >> 4) - (val >> 4);
if (al & 0x10)
{
al -= 6;
ah--;
}
if (ah & 0x10)
ah -= 6;
flag.carry = (diff < 0x100);
flag.zero_ = flag.negative_ = cast(ubyte)diff;
accumulator = cast(ubyte)((ah << 4) + (al & 0x0F));
accumulator = cast(ubyte)a;
}
final void hex_addWithCarry(ubyte val)