6502/65816.js
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added support for more addressing modes for SBC

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Preston Skupinski 2011-05-07 22:42:11 -04:00
parent e65caf36ec
commit c716e6e2f0
1 changed files with 103 additions and 0 deletions
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103
cpu.js
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@ -85,6 +85,11 @@ function CPU_65816() {
0x7d : ADC_absolute_indexed_x,
0x79 : ADC_absolute_indexed_y,
0x75 : ADC_direct_page_indexed_x, 0xe9 : SBC_const,
0xed : SBC_absolute, 0xe5 : SBC_direct_page,
0xf2 : SBC_direct_page_indirect,
0xfd : SBC_absolute_indexed_x,
0xf9 : SBC_absolute_indexed_y,
0xe1 : SBC_direct_page_indexed_x,
0xc9 : CMP_const, 0xc5 : CMP_direct_page,
0xcd : CMP_absolute, 0xe0 : CPX_const,
0xec : CPX_absolute, 0xe4 : CPX_direct_page,
@ -435,6 +440,104 @@ var SBC_const = {
}
};
var SBC_direct_page = {
bytes_required:function() {
return 2;
},
execute:function(cpu, bytes) {
var location = bytes[0] + cpu.r.d;
if(cpu.p.m) {
SBC_const.execute(cpu, [cpu.mmu.read_byte(location)]);
} else {
var low_byte = cpu.mmu.read_byte(location);
var high_byte = cpu.mmu.read_byte(location+1);
SBC_const.execute(cpu, [low_byte, high_byte]);
}
}
};
var SBC_absolute = {
bytes_required:function() {
return 3;
},
execute:function(cpu, bytes) {
var location = (bytes[1]<<8)|bytes[0];
if(cpu.p.m) {
SBC_const.execute(cpu, [cpu.mmu.read_byte(location)]);
} else {
var low_byte = cpu.mmu.read_byte(location);
var high_byte = cpu.mmu.read_byte(location+1);
SBC_const.execute(cpu, [low_byte, high_byte]);
}
}
};
var SBC_direct_page_indirect = {
bytes_required:function() {
return 2;
},
execute:function(cpu, bytes) {
var location = bytes[0] + cpu.r.d;
var low_byte_loc = cpu.mmu.read_byte(location);
var high_byte_loc = cpu.mmu.read_byte(location+1);
var absolute_location = (high_byte_loc<<8) | low_byte_loc;
if(cpu.p.m) {
SBC_const.execute(cpu, [cpu.mmu.read_byte(absolute_location)]);
} else {
var low_byte = cpu.mmu.read_byte(absolute_location);
var high_byte = cpu.mmu.read_byte(absolute_location+1);
SBC_const.execute(cpu, [low_byte, high_byte]);
}
}
};
var SBC_absolute_indexed_x = {
bytes_required:function() {
return 3;
},
execute:function(cpu, bytes) {
SBC_absolute.execute(cpu, ((bytes[1]<<8)|bytes[0])+cpu.r.x);
}
};
var SBC_absolute_indexed_y = {
bytes_required:function() {
return 3;
},
execute:function(cpu, bytes) {
SBC_absolute.execute(cpu, ((bytes[1]<<8)|bytes[0])+cpu.r.y);
}
};
var SBC_direct_page_indexed_x = {
bytes_required:function() {
return 2;
},
execute:function(cpu, bytes) {
SBC_direct_page.execute(cpu, bytes[0]+cpu.r.x);
}
};
var SBC_direct_page_indirect = {
bytes_required:function() {
return 2;
},
execute:function(cpu, bytes) {
var location = bytes[0] + cpu.r.d;
var low_byte_loc = cpu.mmu.read_byte(location);
var high_byte_loc = cpu.mmu.read_byte(location+1);
var absolute_location = (high_byte_loc<<8) | low_byte_loc;
if(cpu.p.m) {
SBC_const.execute(cpu, [cpu.mmu.read_byte(absolute_location)]);
} else {
var low_byte = cpu.mmu.read_byte(absolute_location);
var high_byte = cpu.mmu.read_byte(absolute_location+1);
SBC_const.execute(cpu, [low_byte, high_byte]);
}
}
};
var ADC_const = {
bytes_required:function(cpu) {
if(cpu.p.m) {