Apple-2-Tools/bradgrantham-apple2e
1
0
Fork 0
mirror of https://github.com/bradgrantham/apple2e.git synced 2024-06-16 08:29:31 +00:00
Code Issues Projects Releases Wiki Activity

another SBC and another CPY

Browse Source
This commit is contained in:
Brad Grantham 2016-11-06 14:10:46 -08:00
parent 8a0a95e98e
commit 484c94df98
1 changed files with 24 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
apple2e.cpp
View File

@ -573,6 +573,19 @@ struct CPU6502
break;
}
case 0xED: {
int addr = read_pc_inc(bus) + read_pc_inc(bus) * 256;
if(debug & DEBUG_DECODE) printf("SBC %04X\n", addr);
unsigned char imm = bus.read(addr);
int borrow = isset(C) ? 0 : 1;
flag_change(C, !(a < imm - borrow));
a = a - imm - borrow;
flag_change(N, a & 0x80);
flag_change(V, isset(C) != isset(N));
flag_change(Z, a == 0);
break;
}
case 0xE9: {
unsigned char imm = read_pc_inc(bus);
if(debug & DEBUG_DECODE) printf("SBC %02X\n", imm);
@ -809,6 +822,17 @@ struct CPU6502
break;
}
case 0xCC: {
int addr = read_pc_inc(bus) + read_pc_inc(bus) * 256;
if(debug & DEBUG_DECODE) printf("CPY %04X\n", addr);
unsigned char imm = bus.read(addr);
flag_change(C, imm <= a);
imm = a - imm;
flag_change(N, imm & 0x80);
flag_change(Z, imm == 0);
break;
}
case 0xC0: {
unsigned char imm = read_pc_inc(bus);
if(debug & DEBUG_DECODE) printf("CPY %02X\n", imm);