6502/65816.js
1
0
Fork 0
mirror of https://github.com/pskupinski/65816.js.git synced 2024-06-06 14:29:28 +00:00
Code Issues Projects Releases Wiki Activity

added MVN and MVP

Browse Source
This commit is contained in:
Preston Skupinski 2011-05-11 01:05:31 -04:00
parent fc55d92515
commit 5347ced894
2 changed files with 107 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

87
cpu.js
View File

@ -127,7 +127,8 @@ function CPU_65816() {
0xda : PHX, 0xfa : PLX, 0x08 : PHP, 0x28 : PLP,
0xf4 : PEA, 0xd4 : PEI, 0x8b : PHB, 0xab : PLB,
0x4b : PHK, 0x0b : PHD, 0x2b : PLD, 0x62 : PER,
0x20 : JSR, 0x60 : RTS, 0x22 : JSL, 0x6b : RTL };
0x20 : JSR, 0x60 : RTS, 0x22 : JSL, 0x6b : RTL,
0x54 : MVN, 0x44 : MVP };
/**
* Take a raw hex string representing the program and execute it.
@ -206,6 +207,90 @@ var MMU = {
}
};
// 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 = {
bytes_required:function() {
return 3;
},
execute:function(cpu, bytes) {
// TODO: One piece of reference material I've read claims that this
// operation should always work with a 16-bit accumulator even if in
// emulation mode or the m bit is set to 1, in those cases it claims that
// you should concatenate the B "hidden" register with A. I'm going to
// need to test this claim out somehow.
var b = cpu.mmu.read_byte_long(cpu.r.x,bytes[1]);
cpu.r.dbr = bytes[0];
cpu.mmu.store_byte(cpu.r.y, b);
cpu.r.x++;
cpu.r.y++;
if(cpu.p.x) {
cpu.r.x &= 0x00ff;
cpu.r.y &= 0x00ff;
} else {
cpu.r.x &= 0xffff;
cpu.r.y &= 0xffff;
}
if(cpu.r.a!=0) {
cpu.r.a--;
cpu.r.pc-=3;
} else {
if(cpu.p.m)
cpu.r.a = 0xff;
else
cpu.r.a = 0xffff;
}
}
};
// MVP is a really weird instruction, until the accumulator reaches $FFFF MVP
// will keep decrementing the program counter to have it continue to execute.
var MVP = {
bytes_required:function() {
return 3;
},
execute:function(cpu, bytes) {
// TODO: One piece of reference material I've read claims that this
// operation should always work with a 16-bit accumulator even if in
// emulation mode or the m bit is set to 1, in those cases it claims that
// you should concatenate the B "hidden" register with A. I'm going to
// need to test this claim out somehow.
var b = cpu.mmu.read_byte_long(cpu.r.x,bytes[1]);
cpu.r.dbr = bytes[0];
cpu.mmu.store_byte(cpu.r.y,b);
var index_register_wrap;
if(cpu.p.x) {
index_register_wrap = 0xff;
} else {
index_register_wrap = 0xffff;
}
if(cpu.r.y===index_register_wrap) {
cpu.r.y = 0;
} else {
cpu.r.y--;
}
if(cpu.r.x===index_register_wrap) {
cpu.r.x = 0;
} else {
cpu.r.x--;
}
if(cpu.r.a!=0) {
cpu.r.pc-=3;
cpu.r.a--;
} else {
if(cpu.p.m)
cpu.r.a = 0xff;
else
cpu.r.a = 0xffff;
}
}
};
var JSL = {
bytes_required:function() {
return 4;

21
test/tests.js
View File

@ -22,6 +22,27 @@ function run_tests() {
test_sbc();
test_cmp();
test_subroutines();
test_mvn_and_mvp();
}
function test_mvn_and_mvp() {
test("Test a short example program for MVP", function() {
var cpu = new CPU_65816();
cpu.execute("18fbe230a9ab8dff0fa9cd8d0010c230a90100a20010a00020440000");
equals(cpu.r.a, 0xffff, "After executing the example program the "+
"accumulator should've underflowed and "+
"resulted in 0xffff.");
equals(cpu.r.x, 0x0ffe, "After executing the example program the x "+
"register should be 0x0ffe.");
equals(cpu.r.y, 0x1ffe, "After executing the example program the y "+
"register should be 0x1ffe.");
var byte_one = cpu.mmu.read_byte(0x1fff);
var byte_two = cpu.mmu.read_byte(0x2000);
equals(byte_one, 0xab, "After executing the example program 0x001fff "+
"in memory should contain 0xab.");
equals(byte_two, 0xcd, "After executing the example program 0x002000 "+
"in memory should contain 0xcd.");
});
}
function test_subroutines() {