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Update NEC DSP core to correctly generate the ov1 and s1 alu

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flags (and hence, SGN register contents). [Lord Nightmare,
Segher, byuu, Cydrak]
This commit is contained in:
Jonathan Gevaryahu 2011-07-03 21:03:01 +00:00
parent 5975bf4501
commit 6f893c29f1
2 changed files with 11 additions and 11 deletions
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21
src/emu/cpu/upd7725/upd7725.c
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@ -375,7 +375,7 @@ void necdsp_device::exec_op(UINT32 opcode) {
case 4: regs.idb = regs.dp; break;
case 5: regs.idb = regs.rp; break;
case 6: regs.idb = m_data->read_word(regs.rp<<1); break;
case 7: regs.idb = 0x8000 - regs.flaga.s1; break;
case 7: regs.idb = 0x8000 - regs.flaga.s1; break; //SGN
case 8: regs.idb = regs.dr; regs.sr.rqm = 1; break;
case 9: regs.idb = regs.dr; break;
case 10: regs.idb = regs.sr; break;
@ -428,12 +428,13 @@ void necdsp_device::exec_op(UINT32 opcode) {
flag.s0 = (r & 0x8000);
flag.z = (r == 0);
flag.ov0pp = flag.ov0p;
flag.ov0p = flag.ov0;
switch(alu) {
case 1: case 2: case 3: case 10: case 13: case 14: case 15: {
flag.c = 0;
flag.ov0 = 0;
flag.ov1 = 0;
flag.ov0 = flag.ov0p = flag.ov0pp = 0; // ASSUMPTION: previous ov0 values are nulled here to make ov1 zero
break;
}
case 4: case 5: case 6: case 7: case 8: case 9: {
@ -446,25 +447,23 @@ void necdsp_device::exec_op(UINT32 opcode) {
flag.ov0 = (q ^ r) & (q ^ p) & 0x8000;
flag.c = (r > q);
}
if(flag.ov0) {
flag.s1 = flag.ov1 ^ !(r & 0x8000);
flag.ov1 = !flag.ov1;
}
break;
}
case 11: {
flag.c = q & 1;
flag.ov0 = 0;
flag.ov1 = 0;
flag.ov0 = flag.ov0p = flag.ov0pp = 0; // ASSUMPTION: previous ov0 values are nulled here to make ov1 zero
break;
}
case 12: {
flag.c = q >> 15;
flag.ov0 = 0;
flag.ov1 = 0;
flag.ov0 = flag.ov0p = flag.ov0pp = 0; // ASSUMPTION: previous ov0 values are nulled here to make ov1 zero
break;
}
}
// flag.ov1 is only set if the number of overflows of the past 3 opcodes (of type 4,5,6,7,8,9) is odd
flag.ov1 = (flag.ov0 + flag.ov0p + flag.ov0pp) & 1;
// flag.s1 is based on ov1: s1 = ov1 ^ s0;
flag.s1 = flag.ov1 ^ flag.s0;
switch(asl) {
case 0: regs.a = r; regs.flaga = flag; break;

1
src/emu/cpu/upd7725/upd7725.h
View File

@ -97,6 +97,7 @@ private:
struct Flag
{
bool s1, s0, c, z, ov1, ov0;
bool ov0p, ov0pp; // these are the previous states of the ov0 bit and are used for updating ov1
inline operator unsigned() const
{