6502
/
65816.js
mirror of https://github.com/pskupinski/65816.js.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

direct page addressing when using an index register must overflow to 0x0000 and not be allowed to exceed 0xffff, so 0xfff0+0x12 should result in an address of 0x02

This commit is contained in:
Preston Skupinski 2011-04-30 23:54:07 -04:00
parent 67b19ee43a
commit 44696ed8ce
1 changed files with 84 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

91
cpu.js
View File

@ -150,8 +150,19 @@ var STZ_direct_page_indexed_x = {
if(cpu.p.m===1) {
cpu.mmu.store_byte(location, 0);
} else {
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
cpu.mmu.store_byte(location, 0);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
cpu.mmu.store_byte(location, 0);
cpu.mmu.store_byte(location+1, 0);
}
}
};
@ -165,8 +176,19 @@ var LDA_direct_page_indexed_x = {
if(cpu.p.m===1) {
cpu.r.a = cpu.mmu.read_byte(location);
} else {
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
var high_byte = cpu.mmu.read_byte(location);
var low_byte = cpu.mmu.read_byte(location+1);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
var low_byte = cpu.mmu.read_byte(location);
cpu.r.a = high_byte | low_byte;
}
if(cpu.r.a===0) {
@ -272,8 +294,19 @@ var LDY_direct_page_indexed_x = {
if(cpu.p.m===1) {
cpu.r.y = cpu.mmu.read_byte(location);
} else {
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
var high_byte = cpu.mmu.read_byte(location);
var low_byte = cpu.mmu.read_byte(location+1);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
var low_byte = cpu.mmu.read_byte(location);
cpu.r.y = high_byte | low_byte;
}
if(cpu.r.a===0) {
@ -427,8 +460,19 @@ var STA_direct_page_indexed_x = {
} else {
var high_byte = cpu.r.a & 0xFF00;
var low_byte = cpu.r.a & 0x00FF;
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
cpu.mmu.store_byte(location, low_byte);
cpu.mmu.store_byte(location+1, high_byte);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
cpu.mmu.store_byte(location, high_byte);
}
}
};
@ -495,8 +539,19 @@ var STY_direct_page_indexed_x = {
} else {
var high_byte = cpu.r.y & 0xFF00;
var low_byte = cpu.r.y & 0x00FF;
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
cpu.mmu.store_byte(location, low_byte);
cpu.mmu.store_byte(location+1, high_byte);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
cpu.mmu.store_byte(location, high_byte);
}
}
};
@ -546,8 +601,19 @@ var STX_direct_page_indexed_y = {
} else {
var high_byte = cpu.r.x & 0xFF00;
var low_byte = cpu.r.x & 0x00FF;
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
cpu.mmu.store_byte(location, low_byte);
cpu.mmu.store_byte(location+1, high_byte);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
cpu.mmu.store_byte(location, high_byte);
}
}
};
@ -632,8 +698,19 @@ var LDX_direct_page_indexed_y = {
if(cpu.p.x===1) {
cpu.r.x = cpu.mmu.read_byte(location);
} else {
// Check for overflow.
var overflow_check = location - 0xffff;
if(overflow_check > 0) {
location = overflow_check-1;
}
var high_byte = cpu.mmu.read_byte(location);
var low_byte = cpu.mmu.read_byte(location+1);
// Check for potential overflow again.
if(location===0xffff) {
location = 0;
} else {
location++;
}
var low_byte = cpu.mmu.read_byte(location);
cpu.r.x = high_byte | low_byte;
}
if(cpu.r.x===0) {