necdsp: improve OV1/S1 flag calculations

necdsp: improve OV1/S1 flag calculations

bsnes/snes/chip/necdsp/necdsp.cpp

@@ -100,6 +100,7 @@ void NECDSP::exec_op(uint24 opcode) {
 
     flag.s0 = (r & 0x8000);
     flag.z = (r == 0);
+    if (!flag.ov1) flag.s1 = flag.s0;
 
     switch(alu) {
       case  1: case  2: case  3: case 10: case 13: case 14: case 15: {
@@ -111,17 +112,14 @@ void NECDSP::exec_op(uint24 opcode) {
       case  4: case  5: case  6: case  7: case  8: case  9: {
         if(alu & 1) {
           //addition
-          flag.ov0 = (q ^ r) & ~(q ^ p) & 0x8000;
+          flag.ov0 = (q ^ r) & (p ^ r) & 0x8000;
           flag.c = (r < q);
         } else {
           //subtraction
           flag.ov0 = (q ^ r) & (q ^ p) & 0x8000;
           flag.c = (r > q);
         }
-        if(flag.ov0) {
+        flag.ov1 = (flag.ov0 & flag.ov1) ? (flag.s1 == flag.s0) : (flag.ov0 | flag.ov1);
-          flag.s1 = flag.ov1 ^ !(r & 0x8000);
-          flag.ov1 = !flag.ov1;
-        }
         break;
       }
       case 11: {
@@ -146,15 +144,16 @@ void NECDSP::exec_op(uint24 opcode) {
 
   exec_ld((idb << 6) + dst);
 
+  if (dst != 4) {
     switch(dpl) {
       case 1: regs.dp = (regs.dp & 0xf0) + ((regs.dp + 1) & 0x0f); break;  //DPINC
       case 2: regs.dp = (regs.dp & 0xf0) + ((regs.dp - 1) & 0x0f); break;  //DPDEC
       case 3: regs.dp = (regs.dp & 0xf0); break;  //DPCLR
     }
-
     regs.dp ^= dphm << 4;
+  }
 
-  if(rpdcr) regs.rp--;
+  if(rpdcr && dst != 5) regs.rp--;
 }
 
 void NECDSP::exec_rt(uint24 opcode) {

bsnes/snes/smp/memory/memory.cpp

@@ -80,14 +80,12 @@ alwaysinline void SMP::op_buswrite(uint16 addr, uint8 data) {
         if(regs.p.p) break;  //writes only valid when P flag is clear
 
         status.clock_speed     = (data >> 6) & 3;
-        status.timer_speed     = (data >> 4) & 3;
+        status.ram_speed       = (data >> 4) & 3;
         status.timers_enabled  = data & 0x08;
         status.ram_disabled    = data & 0x04;
         status.ram_writable    = data & 0x02;
         status.timers_disabled = data & 0x01;
 
-        status.timer_step = (1 << status.clock_speed) + (2 << status.timer_speed);
-
         t0.sync_stage1();
         t1.sync_stage1();
         t2.sync_stage1();
@@ -176,23 +174,29 @@ alwaysinline void SMP::op_buswrite(uint16 addr, uint8 data) {
   ram_write(addr, data);
 }
 
+unsigned SMP::speed(uint16 addr) const {
+  if((addr & 0xfff0) == 0x00f0) return status.clock_speed;
+  if(addr >= 0xffc0 && status.iplrom_enabled) return status.clock_speed;
+  return status.ram_speed;
+}
+
 void SMP::op_io() {
   add_clocks(24);
-  cycle_edge();
+  cycle_edge(status.clock_speed);
 }
 
 uint8 SMP::op_read(uint16 addr) {
   add_clocks(12);
   uint8 r = op_busread(addr);
   add_clocks(12);
-  cycle_edge();
+  cycle_edge(speed(addr));
   return r;
 }
 
 void SMP::op_write(uint16 addr, uint8 data) {
   add_clocks(24);
   op_buswrite(addr, data);
-  cycle_edge();
+  cycle_edge(speed(addr));
 }
 
 #endif

bsnes/snes/smp/memory/memory.hpp

@@ -4,6 +4,8 @@ void ram_write(uint16 addr, uint8 data);
 uint8 op_busread(uint16 addr);
 void op_buswrite(uint16 addr, uint8 data);
 
+alwaysinline unsigned speed(uint16 addr) const;
+
 void op_io();
 debugvirtual uint8 op_read(uint16 addr);
 debugvirtual void op_write(uint16 addr, uint8 data);

bsnes/snes/smp/serialization.cpp

@@ -4,12 +4,8 @@ void SMP::serialize(serializer &s) {
   Processor::serialize(s);
   SMPcore::core_serialize(s);
 
-  s.integer(status.clock_counter);
-  s.integer(status.dsp_counter);
-  s.integer(status.timer_step);
-
   s.integer(status.clock_speed);
-  s.integer(status.timer_speed);
+  s.integer(status.ram_speed);
   s.integer(status.timers_enabled);
   s.integer(status.ram_disabled);
   s.integer(status.ram_writable);

bsnes/snes/smp/smp.cpp

@@ -76,13 +76,9 @@ void SMP::reset() {
     memory::apuram.write(i, 0x00);
   }
 
-  status.clock_counter = 0;
-  status.dsp_counter = 0;
-  status.timer_step = 3;
-
   //$00f0
   status.clock_speed = 0;
-  status.timer_speed = 0;
+  status.ram_speed = 0;
   status.timers_enabled = true;
   status.ram_disabled = false;
   status.ram_writable = true;

bsnes/snes/smp/smp.hpp

@@ -21,14 +21,9 @@ private:
   #include "timing/timing.hpp"
 
   struct {
-    //timing
-    unsigned clock_counter;
-    unsigned dsp_counter;
-    unsigned timer_step;
-
     //$00f0
     uint8 clock_speed;
-    uint8 timer_speed;
+    uint8 ram_speed;
     bool timers_enabled;
     bool ram_disabled;
     bool ram_writable;

bsnes/snes/smp/timing/timing.cpp

@@ -9,25 +9,22 @@ void SMP::add_clocks(unsigned clocks) {
   if(clock > +(768 * 24 * (int64)24000000)) synchronize_cpu();
 }
 
-void SMP::cycle_edge() {
+void SMP::cycle_edge(unsigned speed) {
-  t0.tick();
+  static const uint8 wait_states[] = {0, 24*1, 24*4, 24*9};
-  t1.tick();
+
-  t2.tick();
+  unsigned ticks = 1 << speed;
+  t0.tick(ticks);
+  t1.tick(ticks);
+  t2.tick(ticks);
 
-  //TEST register S-SMP speed control
   //24 clocks have already been added for this cycle at this point
-  switch(status.clock_speed) {
+  if(speed) add_clocks(wait_states[speed]);
-    case 0: break;                       //100% speed
-    case 1: add_clocks(24); break;       // 50% speed
-    case 2: while(true) add_clocks(24);  //  0% speed -- locks S-SMP
-    case 3: add_clocks(24 * 9); break;   // 10% speed
-  }
 }
 
 template<unsigned timer_frequency>
-void SMP::sSMPTimer<timer_frequency>::tick() {
+void SMP::sSMPTimer<timer_frequency>::tick(unsigned step) {
   //stage 0 increment
-  stage0_ticks += smp.status.timer_step;
+  stage0_ticks += step;
   if(stage0_ticks < timer_frequency) return;
   stage0_ticks -= timer_frequency;
 

bsnes/snes/smp/timing/timing.hpp

@@ -9,13 +9,13 @@ public:
   bool enabled;
   uint8 target;
 
-  void tick();
+  void tick(unsigned step);
   void sync_stage1();
 };
 
-sSMPTimer<192> t0;
+sSMPTimer<64> t0;
-sSMPTimer<192> t1;
+sSMPTimer<64> t1;
-sSMPTimer< 24> t2;
+sSMPTimer< 8> t2;
 
 alwaysinline void add_clocks(unsigned clocks);
-alwaysinline void cycle_edge();
+alwaysinline void cycle_edge(unsigned speed);