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65816.js
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fixed the emulation mode stack register and stack behavior to be a bit more accurate

This commit is contained in:
Preston Skupinski 2011-05-12 00:57:29 -04:00
parent b4f795f368
commit e1f33e4af4
2 changed files with 22 additions and 11 deletions
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29
cpu.js
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@ -22,10 +22,10 @@ function CPU_65816() {
x:0, // X Index Register
y:0, // Y Index Register
d:0, // Direct Page Register
s:0x1ff, // Stack Pointer
s:0xff, // Stack Pointer
pc:0, // Program Counter
dbr:0, // Data Bank Register
k:0 // Program Bank Register
k:0 // Program Bank Register
};
// P register flags.
@ -175,19 +175,26 @@ var MMU = {
memory: { 0: {} },
pull_byte: function() {
if(this.cpu.p.e&&(this.cpu.r.s===0x1ff)) {
this.cpu.r.s = 0x100;
return this.memory[this.cpu.r.dbr][this.cpu.r.s];
if(this.cpu.p.e) {
if(this.cpu.r.s===0xff) {
this.cpu.r.s = 0;
return this.memory[this.cpu.r.dbr][0x100|this.cpu.r.s];
} else {
return this.memory[this.cpu.r.dbr][0x100|(++this.cpu.r.s)];
}
} else {
return this.memory[this.cpu.r.dbr][++this.cpu.r.s];
}
},
push_byte: function(b) {
if(this.cpu.p.e&&(this.cpu.r.s===0x100)) {
var result = this.memory[this.cpu.r.dbr][this.cpu.r.s];
this.cpu.r.s = 0x1ff;
return result;
if(this.cpu.p.e) {
if(this.cpu.r.s===0) {
this.memory[this.cpu.r.dbr][0x100|this.cpu.r.s] = b;
this.cpu.r.s = 0xff;
} else {
this.memory[this.cpu.r.dbr][0x100|(this.cpu.r.s--)] = b;
}
} else {
this.memory[this.cpu.r.dbr][this.cpu.r.s--] = b;
}
@ -3463,9 +3470,13 @@ var XCE = {
var low_byte = cpu.r.a & 0x00ff;
cpu.r.a = low_byte;
cpu.r.b = high_byte;
cpu.r.s &= 0xff;
} else {
// Switching to native mode.
cpu.r.a = (cpu.r.b<<8) | cpu.r.a;
cpu.p.m = 1;
cpu.p.x = 1;
cpu.r.s |= 0x100;
}
}
};

4
test/tests.js
View File

@ -32,8 +32,8 @@ function test_emulation_mode() {
"causes the stack register to pull from 0x100.", function() {
var cpu = new CPU_65816();
cpu.execute("a9fe8d0001a90068");
equals(cpu.r.s, 0x100, "The stack register should be 0x100 after the "+
"pull operation.");
equals(cpu.r.s, 0, "The stack register should be 0 after the pull "+
"operation.");
equals(cpu.r.a, 0xfe, "The accumulator should be 0xfe after the pull "+
"operation.");
});