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Fix for [sp+n] instruction length, DIV EXtension, EX evaluation order and option for shift behaviour #49

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Fix for [sp+n] instruction length, DIV EXtension, EX evaluation order and option for shift behaviour #49

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b72734c
fixed instruction length for sp+n
orlof Mar 12, 2016
d37b723
Changed the evaluation order if b is ex. e.g. SET ex, 3; SHR ex, 1 ->…
orlof Mar 15, 2016
e214df4
Removed rotate behavior from shift instructions
orlof Mar 15, 2016
27c2161
made shift instruction configurable. you can limit shift distance to …
Mar 17, 2016
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83 changes: 51 additions & 32 deletions DevCPU/src/devcpu/emulation/DCPU.java
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,8 @@
*/
public class DCPU
{
private static final boolean SHIFT_DISTANCE_5_BITS = true;

private static final boolean DISASSEMBLE = false;
public char[] ram = new char[65536];
public char pc;
Expand Down Expand Up @@ -225,14 +227,14 @@ public static int getInstructionLength(char opcode) {
cmd = opcode >> 5 & 0x1F;
if (cmd > 0) {
int atype = opcode >> 10 & 0x3F;
if (((atype & 0xF8) == 16) || (atype == 31) || (atype == 30)) len++;
if (((atype & 0xF8) == 16) || (atype == 26) || (atype == 31) || (atype == 30)) len++;
}
}
else {
int atype = opcode >> 5 & 0x1F;
int btype = opcode >> 10 & 0x3F;
if (((atype & 0xF8) == 16) || (atype == 31) || (atype == 30)) len++;
if (((btype & 0xF8) == 16) || (btype == 31) || (btype == 30)) len++;
if (((atype & 0xF8) == 16) || (atype == 26) || (atype == 31) || (atype == 30)) len++;
if (((btype & 0xF8) == 16) || (atype == 26) || (btype == 31) || (btype == 30)) len++;
}
return len;
}
Expand Down Expand Up @@ -384,45 +386,49 @@ public void tick() {
case 2:{ //ADD
cycles++;
int val = b + a;
b = (char)val;
set(baddr, (char)val);
ex = (char)(val >> 16);
break;
return;
}case 3:{ //SUB
cycles++;
int val = b - a;
b = (char)val;
set(baddr, (char)val);
ex = (char)(val >> 16);
break;
return;
}case 4:{ //MUL
cycles++;
int val = b * a;
b = (char)val;
set(baddr, (char)val);
ex = (char)(val >> 16);
break;
return;
}case 5:{ //MLI
cycles++;
int val = (short)b * (short)a;
b = (char)val;
set(baddr, (char)val);
ex = (char)(val >> 16);
break;
return;
}case 6:{ //DIV
cycles += 2;
if (a == 0) {
b = ex = 0;
set(baddr, (char) 0);
ex = 0;
return;
} else {
b /= a;
ex = (char)((b << 16) / a);
set(baddr, (char) (b / a));
ex = (char) (((long) b << 16) / a);
return;
}
break;
}case 7:{ //DVI
cycles += 2;
if (a == 0) {
b = ex = 0;
set(baddr, (char) 0);
ex = 0;
return;
} else {
b = (char)((short)b / (short)a);
ex = (char)(((short)b << 16) / (short)a);
set(baddr, (char) ((short) b / (short) a));
ex = (char) ((b << 16) / ((short) a));
return;
}
break;
}case 8: //MOD
cycles += 2;
if (a == 0)
Expand All @@ -449,17 +455,30 @@ public void tick() {
b = (char)(b ^ a);
break;
case 13: //SHR
ex = (char)(b << 16 >> a);
b = (char)(b >>> a);
break;
if(!SHIFT_DISTANCE_5_BITS && a > 31) {
set(baddr, (char) 0);
ex = (char) 0;
} else {
set(baddr, (char) (b >>> a));
ex = (char) (b << 16 >>> a);
}
return;
case 14: //ASR
ex = (char)((short)b << 16 >>> a);
b = (char)((short)b >> a);
break;
if(!SHIFT_DISTANCE_5_BITS && a > 31) {
a = 31;
}
set(baddr, (char)((short)b >> a));
ex = (char)(b << 16 >> a);
return;
case 15: //SHL
ex = (char)(b << a >> 16);
b = (char)(b << a);
break;
if(!SHIFT_DISTANCE_5_BITS && a > 31) {
set(baddr, (char) 0);
ex = (char) 0;
} else {
set(baddr, (char) (b << a));
ex = (char) (b << a >> 16);
}
return;
case 16: //IFB
cycles++;
if ((b & a) == 0) skip();
Expand Down Expand Up @@ -495,15 +514,15 @@ public void tick() {
case 26:{ //ADX
cycles++;
int val = b + a + ex;
b = (char)val;
set(baddr, (char)val);
ex = (char)(val >> 16);
break;
return;
}case 27:{ //SBX
cycles++;
int val = b - a + ex;
b = (char)val;
set(baddr, (char)val);
ex = (char)(val >> 16);
break;
return;
}case 30: //STI
b = a;
set(baddr, b);
Expand Down