6502/65816.js
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added basic working interrupt handling and the BRK and RTI operations.

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Preston Skupinski 2011-05-14 23:17:28 -04:00
parent d446c727bf
commit e37b40fb76
1 changed files with 116 additions and 2 deletions
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118
cpu.js
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@ -40,7 +40,10 @@ function CPU_65816() {
v:0, // Overflow (1 = overflow)
n:0 // Negative (1 = negative)
};
this.interrupt = 0; // 0 = no interrupt. 1 = NMI. 2 = RESET. 3 = ABORT.
// 4 = COP. 5 = IRQ. 6 = BRK.
this.mmu = MMU;
this.mmu.cpu = this;
@ -159,7 +162,7 @@ function CPU_65816() {
0xf4 : PEA, 0xd4 : PEI, 0x8b : PHB, 0xab : PLB,
0x4b : PHK, 0x0b : PHD, 0x2b : PLD, 0x62 : PER,
0x20 : JSR, 0x60 : RTS, 0x22 : JSL, 0x6b : RTL,
0x54 : MVN, 0x44 : MVP };
0x54 : MVN, 0x44 : MVP, 0x00 : BRK, 0x40 : RTI };
/**
* Take a raw hex string representing the program and execute it.
@ -174,6 +177,81 @@ function CPU_65816() {
var executing = true;
while(executing) {
if(this.interrupt&&(!this.p.i|(this.interrupt===1))) {
// Load the related interrupt vector in page 0xff of bank zero.
if(!this.p.e) {
this.mmu.push_byte(this.r.k);
}
this.mmu.push_byte(this.r.pc>>8);
this.mmu.push_byte(this.r.pc&0xff);
var p_byte = (cpu.p.n<<7)|(cpu.p.v<<6)|(cpu.p.m<<5)|(cpu.p.x<<4)|
(cpu.p.d<<3)|(cpu.p.i<<2)|(cpu.p.z<<1)|cpu.p.c;
cpu.mmu.push_byte(p_byte);
if(!this.p.e)
this.p.d = 0;
this.p.i = 1;
this.r.k = 0;
// Look for where to jump to for the interrupt.
if(this.p.e) {
// NMI
if(this.interrupt===1) {
var low_byte = this.mmu.read_byte_long(0xfffa, 0);
var high_byte = this.mmu.read_byte_long(0xfffb, 0);
this.r.pc = (high_byte<<8)|low_byte;
// RESET
} else if(this.interrupt===2) {
var low_byte = this.mmu.read_byte_long(0xfffc, 0);
var high_byte = this.mmu.read_byte_long(0xfffd, 0);
this.r.pc = (high_byte<<8)|low_byte;
// ABORT
} else if(this.interrupt===3) {
var low_byte = this.mmu.read_byte_long(0xfff8, 0);
var high_byte = this.mmu.read_byte_long(0xfff9, 0);
this.r.pc = (high_byte<<8)|low_byte;
// COP
} else if(this.interrupt===4) {
var low_byte = this.mmu.read_byte_long(0xfff4, 0);
var high_byte = this.mmu.read_byte_long(0xfff5, 0);
this.r.pc = (high_byte<<8)|low_byte;
// IRQ or BRK
} else if(this.interrupt===5|this.interrupt==6) {
var low_byte = this.mmu.read_byte_long(0xfffe, 0);
var high_byte = this.mmu.read_byte_long(0xffff, 0);
this.r.pc = (high_byte<<8)|low_byte;
}
} else {
// NMI
if(this.interrupt===1) {
var low_byte = this.mmu.read_byte_long(0xffea, 0);
var high_byte = this.mmu.read_byte_long(0xffeb, 0);
this.r.pc = (high_byte<<8)|low_byte;
// ABORT
} else if(this.interrupt===3) {
var low_byte = this.mmu.read_byte_long(0xffe8, 0);
var high_byte = this.mmu.read_byte_long(0xffe9, 0);
this.r.pc = (high_byte<<8)|low_byte;
// COP
} else if(this.interrupt===4) {
var low_byte = this.mmu.read_byte_long(0xffe4, 0);
var high_byte = this.mmu.read_byte_long(0xffe5, 0);
this.r.pc = (high_byte<<8)|low_byte;
// IRQ
} else if(this.interrupt===5) {
var low_byte = this.mmu.read_byte_long(0xffee, 0);
var high_byte = this.mmu.read_byte_long(0xffef, 0);
this.r.pc = (high_byte<<8)|low_byte;
// BRK
} else if(this.interrupt===6) {
var low_byte = this.mmu.read_byte_long(0xffe6, 0);
var high_byte = this.mmu.read_byte_long(0xffe7, 0);
this.r.pc = (high_byte<<8)|low_byte;
}
}
this.interrupt = 0;
}
var b = this.mmu.read_byte_long(this.r.pc, this.r.k);
this.r.pc++;
@ -264,6 +342,42 @@ var MMU = {
}
};
var BRK = {
bytes_required:function() {
return 2;
},
execute:function(cpu) {
cpu.interrupt = 6;
if(cpu.p.e)
cpu.p.m = 1;
}
};
var RTI = {
bytes_required:function() {
return 1;
},
execute:function(cpu) {
var p_byte = cpu.mmu.pull_byte();
var pc_low = cpu.mmu.pull_byte();
var pc_high = cpu.mmu.pull_byte();
cpu.r.pc = (pc_high<<8)|pc_low;
cpu.p.c = p_byte & 0x01;
cpu.p.z = (p_byte & 0x02) >> 1;
cpu.p.i = (p_byte & 0x04) >> 2;
cpu.p.d = (p_byte & 0x08) >> 3;
cpu.p.x = (p_byte & 0x10) >> 4;
cpu.p.m = (p_byte & 0x20) >> 5;
cpu.p.v = (p_byte & 0x40) >> 6;
cpu.p.n = p_byte >> 7;
if(!cpu.p.e) {
cpu.r.k = cpu.mmu.pull_byte();
}
}
};
// MVN is a really weird instruction, until the accumulator underflows MVN
// will keep decrementing the program counter to have it continue to execute.
var MVN = {