From ce49928623177f336bbde51ab234b3054e6821e5 Mon Sep 17 00:00:00 2001 From: Lord-Nightmare Date: Sun, 3 Sep 2017 05:16:11 -0400 Subject: upd7725: update ov1 and s1 flag calculation to be correct based on AWJ's nesdev forums post and the original datasheets. [AWJ, Lord Nightmare] --- src/devices/cpu/upd7725/upd7725.cpp | 30 ++++++++---------------------- src/devices/cpu/upd7725/upd7725.h | 6 +++--- 2 files changed, 11 insertions(+), 25 deletions(-) diff --git a/src/devices/cpu/upd7725/upd7725.cpp b/src/devices/cpu/upd7725/upd7725.cpp index 697a8b075b7..f010acc8b0f 100644 --- a/src/devices/cpu/upd7725/upd7725.cpp +++ b/src/devices/cpu/upd7725/upd7725.cpp @@ -119,16 +119,12 @@ void necdsp_device::device_start() save_item(NAME(regs.flaga.z)); save_item(NAME(regs.flaga.ov1)); save_item(NAME(regs.flaga.ov0)); - save_item(NAME(regs.flaga.ov0p)); - save_item(NAME(regs.flaga.ov0pp)); save_item(NAME(regs.flagb.s1)); save_item(NAME(regs.flagb.s0)); save_item(NAME(regs.flagb.c)); save_item(NAME(regs.flagb.z)); save_item(NAME(regs.flagb.ov1)); save_item(NAME(regs.flagb.ov0)); - save_item(NAME(regs.flagb.ov0p)); - save_item(NAME(regs.flagb.ov0pp)); save_item(NAME(regs.tr)); save_item(NAME(regs.trb)); save_item(NAME(regs.dr)); @@ -251,9 +247,7 @@ void necdsp_device::state_string_export(const device_state_entry &entry, std::st regs.flaga.c ? 'C' : 'c', regs.flaga.z ? 'Z' : 'z', regs.flaga.ov1 ? "OV1" : "ov1", - regs.flaga.ov0 ? "OV0" : "ov0", - regs.flaga.ov0p ? "OV0P" : "ov0p", - regs.flaga.ov0pp ? "OV0PP" : "ov0pp"); + regs.flaga.ov0 ? "OV0" : "ov0"); break; case UPD7725_FLAGB: @@ -263,9 +257,7 @@ void necdsp_device::state_string_export(const device_state_entry &entry, std::st regs.flagb.c ? 'C' : 'c', regs.flagb.z ? 'Z' : 'z', regs.flagb.ov1 ? "OV1" : "ov1", - regs.flagb.ov0 ? "OV0" : "ov0", - regs.flagb.ov0p ? "OV0P" : "ov0p", - regs.flagb.ov0pp ? "OV0PP" : "ov0pp"); + regs.flagb.ov0 ? "OV0" : "ov0"); break; } } @@ -442,8 +434,6 @@ void necdsp_device::exec_op(uint32_t opcode) { flag.s1 = 0; flag.ov0 = 0; flag.ov1 = 0; - flag.ov0p = 0; - flag.ov0pp = 0; switch(pselect) { case 0: p = dataRAM[regs.dp]; break; @@ -469,7 +459,7 @@ void necdsp_device::exec_op(uint32_t opcode) { case 9: r = q + 1; p = 1; break; //INC case 10: r = ~q; break; //CMP case 11: r = (q >> 1) | (q & 0x8000); break; //SHR1 (ASR) - case 12: r = (q << 1) | (c ? 1 : 0); break; //SHL1 (ROL) + case 12: r = (q << 1) | (c ? 1 : 0); break; //SHL1 (ROL) case 13: r = (q << 2) | 3; break; //SHL2 case 14: r = (q << 4) | 15; break; //SHL4 case 15: r = (q << 8) | (q >> 8); break; //XCHG @@ -477,13 +467,12 @@ void necdsp_device::exec_op(uint32_t opcode) { flag.s0 = (r & 0x8000); flag.z = (r == 0); - flag.ov0pp = flag.ov0p; - flag.ov0p = flag.ov0; + if (!flag.ov1) flag.s1 = flag.s0; switch(alu) { case 1: case 2: case 3: case 10: case 13: case 14: case 15: { flag.c = 0; - flag.ov0 = flag.ov0p = flag.ov0pp = 0; // ASSUMPTION: previous ov0 values are nulled here to make ov1 zero + flag.ov0 = flag.ov1 = 0; // OV0 and OV1 are cleared by any non-add/sub/nop operation break; } case 4: case 5: case 6: case 7: case 8: case 9: { @@ -496,23 +485,20 @@ void necdsp_device::exec_op(uint32_t opcode) { flag.ov0 = (q ^ r) & (q ^ p) & 0x8000; flag.c = (r > q); } + flag.ov1 = (flag.ov0 & flag.ov1) ? (flag.s1 == flag.s0) : (flag.ov0 | flag.ov1); break; } case 11: { flag.c = q & 1; - flag.ov0 = flag.ov0p = flag.ov0pp = 0; // ASSUMPTION: previous ov0 values are nulled here to make ov1 zero + flag.ov0 = flag.ov1 = 0; // OV0 and OV1 are cleared by any non-add/sub/nop operation break; } case 12: { flag.c = q >> 15; - flag.ov0 = flag.ov0p = flag.ov0pp = 0; // ASSUMPTION: previous ov0 values are nulled here to make ov1 zero + flag.ov0 = flag.ov1 = 0; // OV0 and OV1 are cleared by any non-add/sub/nop operation 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; diff --git a/src/devices/cpu/upd7725/upd7725.h b/src/devices/cpu/upd7725/upd7725.h index 3210c4d6c3a..76cc13b9226 100644 --- a/src/devices/cpu/upd7725/upd7725.h +++ b/src/devices/cpu/upd7725/upd7725.h @@ -119,16 +119,16 @@ protected: private: struct Flag { - bool s1, s0, c, z, ov1, ov0, ov0p, ov0pp; + bool s1, s0, c, z, ov1, ov0; inline operator unsigned() const { - return (s1 << 7) + (s0 << 6) + (c << 5) + (z << 4) + (ov1 << 3) + (ov0 << 2) + (ov0p << 1) + (ov0pp << 0); + return (s1 << 5) + (s0 << 4) + (c << 3) + (z << 2) + (ov1 << 1) + (ov0 << 0); } inline unsigned operator=(unsigned d) { - s1 = d & 0x80; s0 = d & 0x40; c = d & 0x20; z = d & 0x10; ov1 = d & 0x08; ov0 = d & 0x04; ov0p = d & 0x02; ov0pp = d & 0x01; + s1 = d & 0x20; s0 = d & 0x10; c = d & 0x08; z = d & 0x04; ov1 = d & 0x02; ov0 = d & 0x01; return d; } }; -- cgit v1.2.3