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65816.js
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added SBC immediate

This commit is contained in:
Preston Skupinski 2011-05-07 17:45:39 -04:00
parent 047095c8cc
commit 146992b192
2 changed files with 128 additions and 6 deletions
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68
cpu.js
View File

@ -84,7 +84,7 @@ function CPU_65816() {
0x65 : ADC_direct_page, 0x72 : ADC_direct_page_indirect,
0x7d : ADC_absolute_indexed_x,
0x79 : ADC_absolute_indexed_y,
0x75 : ADC_direct_page_indexed_x };
0x75 : ADC_direct_page_indexed_x, 0xe9 : SBC_const };
/**
* Take a raw hex string representing the program and execute it.
@ -163,6 +163,63 @@ var MMU = {
}
};
var SBC_const = {
bytes_required:function(cpu) {
if(cpu.p.m) {
return 2;
} else {
return 3;
}
},
execute:function(cpu, bytes) {
var old_a = cpu.r.a;
if(cpu.p.m) {
cpu.r.a -= bytes[0] - cpu.p.c;
if(cpu.r.a < 0) {
cpu.p.c = 1;
cpu.r.a = 0x100 + cpu.r.a;
} else {
cpu.p.c = 0;
}
cpu.p.n = cpu.r.a >> 7;
// Check for signed overflow.
// If they started with the same sign and then the resulting sign is
// different then we have a signed overflow.
if((!((old_a ^ bytes[0]) & 0x80)) && ((cpu.r.a ^ old_a) & 0x80)) {
cpu.p.v = 1;
} else {
cpu.p.v = 0;
}
} else {
var argument = (bytes[1]<<8)|bytes[0];
cpu.r.a -= argument - cpu.p.c;
if(cpu.r.a < 0) {
cpu.p.c = 1;
cpu.r.a = 0x10000 + cpu.r.a;
} else {
cpu.p.c = 0;
}
cpu.p.n = cpu.r.a >> 15;
// Check for signed overflow.
// If they started with the same sign and then the resulting sign is
// different then we have a signed overflow.
if((!((old_a ^ argument) & 0x8000)) && ((cpu.r.a ^ old_a) & 0x8000)) {
cpu.p.v = 1;
} else {
cpu.p.v = 0;
}
}
if(cpu.r.a===0) {
cpu.p.z = 1;
} else {
cpu.p.z = 0;
}
}
};
var ADC_const = {
bytes_required:function(cpu) {
if(cpu.p.m) {
@ -172,8 +229,8 @@ var ADC_const = {
}
},
execute:function(cpu, bytes) {
var old_a = cpu.r.a;
if(cpu.p.m) {
var old_a = cpu.r.a;
cpu.r.a += bytes[0] + cpu.p.c;
if(cpu.r.a & 0x100) {
cpu.p.c = 1;
@ -192,7 +249,6 @@ var ADC_const = {
cpu.p.v = 0;
}
} else {
var old_a = cpu.r.a;
var argument = (bytes[1]<<8)|bytes[0];
cpu.r.a += argument + cpu.p.c;
if(cpu.r.a & 0x10000) {
@ -272,7 +328,7 @@ var ADC_direct_page_indirect = {
}
};
ADC_absolute_indexed_x = {
var ADC_absolute_indexed_x = {
bytes_required:function() {
return 3;
},
@ -281,7 +337,7 @@ ADC_absolute_indexed_x = {
}
};
ADC_absolute_indexed_y = {
var ADC_absolute_indexed_y = {
bytes_required:function() {
return 3;
},
@ -290,7 +346,7 @@ ADC_absolute_indexed_y = {
}
};
ADC_direct_page_indexed_x = {
var ADC_direct_page_indexed_x = {
bytes_required:function() {
return 2;
},

66
test/tests.js
View File

@ -19,6 +19,72 @@ function run_tests() {
test_sep();
test_branching();
test_adc();
test_sbc();
}
function test_sbc() {
module("SBC");
test("Test normal subtraction of two 8-bit numbers that don't cause a "+
"borrow.", function() {
var cpu = new CPU_65816();
cpu.execute("18fbe23018a901e901");
equals(cpu.r.a, 0, "0x01 - 0x01 should result in zero when using "+
"SBC");
equals(cpu.p.z, 1, "0x01 - 0x01 should set the zero(z) bit when "+
"using SBC");
equals(cpu.p.n, 0, "0x01 - 0x01 should not set the negative(n) bit "+
"when using SBC");
equals(cpu.p.v, 0, "0x01 - 0x01 should not set the overflow(v) bit "+
"when using SBC");
equals(cpu.p.c, 0, "0x01 - 0x01 should not set the carry(c) bit when "+
"using SBC");
});
test("Test normal subtraction of two 16-bit numbers that don't cause a "+
"borrow.", function() {
var cpu = new CPU_65816();
cpu.execute("18fbc23018a90100e90100");
equals(cpu.r.a, 0, "0x0001 - 0x0001 should result in zero when using "+
"SBC");
equals(cpu.p.z, 1, "0x0001 - 0x0001 should set the zero(z) bit when "+
"using SBC");
equals(cpu.p.n, 0, "0x0001 - 0x0001 should not set the negative(n) bit "+
"when using SBC");
equals(cpu.p.v, 0, "0x0001 - 0x0001 should not set the overflow(v) bit "+
"when using SBC");
equals(cpu.p.c, 0, "0x0001 - 0x0001 should not set the carry(c) bit "+
"when using SBC");
});
test("Test subtraction that triggers a borrow with 8-bit numbers",
function() {
var cpu = new CPU_65816();
cpu.execute("18fbe23018a9d0e9ef");
equals(cpu.r.a, 0xe1, "0xd0 - 0xef should set the accumulator to 0xe1 "+
"when using SBC");
equals(cpu.p.n, 1, "0xd0 - 0xef should set the negative(n) bit when "+
"using SBC");
equals(cpu.p.v, 0, "0xd0 - 0xef should not set the overflow(v) bit "+
"when using SBC");
equals(cpu.p.z, 0, "0xd0 - 0xef should not set the zero(z) bit when "+
"using SBC");
equals(cpu.p.c, 1, "0xd0 - 0xef should set the carry(c) bit when "+
"using SBC");
});
test("Test subtraction that triggers a borrow with 16-bit numbers",
function() {
var cpu = new CPU_65816();
cpu.execute("18fbc23018a900d0e900ef");
equals(cpu.r.a, 0xe100, "0xd000 - 0xef00 should set the accumulator to "+
"0xe0ff when using SBC");
equals(cpu.p.n, 1, "0xd000 - 0xef00 should set the negative(n) bit when "+
"using SBC");
equals(cpu.p.v, 0, "0xd000 - 0xef00 should not set the overflow(v) bit "+
"when using SBC");
equals(cpu.p.z, 0, "0xd000 - 0xef00 should not set the zero(z) bit when "+
"using SBC");
equals(cpu.p.c, 1, "0xd000 - 0xef00 should set the carry(c) bit when "+
"using SBC");
});
}
function test_adc() {