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65816.js
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added LDA direct page indirect (0xb2)

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Preston Skupinski 2011-05-01 16:52:48 -04:00
parent 982107a90b
commit 96a8899204
1 changed files with 28 additions and 1 deletions
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29
cpu.js
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@ -48,7 +48,9 @@ function CPU_65816() {
0x58 : CLI, 0xc2 : REP, 0xe2 : SEP,
0xa9 : LDA_const, 0xad : LDA_absolute,
0xa5 : LDA_direct_page, 0xbd : LDA_absolute_indexed_x,
0xb9 : LDA_absolute_indexed_y, 0xa2 : LDX_const,
0xb9 : LDA_absolute_indexed_y,
0xb2 : LDA_direct_page_indirect,
0xa2 : LDX_const,
0xae : LDX_absolute, 0xa6 : LDX_direct_page,
0xa0 : LDY_const, 0xbc : LDY_absolute_indexed_x,
0xb4 : LDY_direct_page_indexed_x,
@ -306,6 +308,31 @@ var STZ_direct_page_indexed_x = {
}
};
var LDA_direct_page_indirect = {
bytes_required:function() {
return 2;
},
execute:function(cpu, bytes) {
var location = bytes[0] + cpu.r.d;
if(cpu.p.m===1) {
var low_byte_loc = cpu.mmu.read_byte(location);
var high_byte_loc = cpu.mmu.read_byte(location+1);
cpu.r.a = cpu.mmu.read_byte(high_byte_loc | low_byte_loc);
} else {
var low_byte_loc = cpu.mmu.read_byte(location);
var high_byte_loc = cpu.mmu.read_byte(location+1);
var absolute_location = high_byte_loc | low_byte_loc;
var low_byte = cpu.mmu.read_byte(absolute_location);
var high_byte = cpu.mmu.read_byte(absolute_location+1);
cpu.r.a = high_byte | low_byte;
}
if(cpu.r.a===0) {
cpu.p.z = 1;
}
// TODO: set the n bit of the p status register
}
};
var LDA_direct_page_indexed_x = {
bytes_required:function() {
return 2;