diff --git a/src/engine/dispatch.h b/src/engine/dispatch.h
index c9d49861d..134230cbf 100644
--- a/src/engine/dispatch.h
+++ b/src/engine/dispatch.h
@@ -292,6 +292,12 @@ class DivDispatch {
      */
     virtual void poke(std::vector<DivRegWrite>& wlist);
 
+    /**
+     * get available registers.
+     * @return an array of C strings, terminated by NULL; or NULL if none available.
+     */
+    virtual const char** getRegisterSheet();
+
     /**
      * initialize this DivDispatch.
      * @param parent the parent DivEngine.
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index be97b86d2..210950e88 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -4775,6 +4775,35 @@ void DivEngine::stop() {
   isBusy.unlock();
 }
 
+void DivEngine::halt() {
+  isBusy.lock();
+  halted=true;
+  isBusy.unlock();
+}
+
+void DivEngine::resume() {
+  isBusy.lock();
+  halted=false;
+  haltOn=DIV_HALT_NONE;
+  isBusy.unlock();
+}
+
+void DivEngine::haltWhen(DivHaltPositions when) {
+  isBusy.lock();
+  halted=false;
+  haltOn=when;
+  isBusy.unlock();
+}
+
+bool DivEngine::isHalted() {
+  return halted;
+}
+
+const char** DivEngine::getRegisterSheet(int sys) {
+  if (sys<0 || sys>=song.systemLen) return NULL;
+  return disCont[sys].dispatch->getRegisterSheet();
+}
+
 void DivEngine::recalcChans() {
   chans=0;
   int chanIndex=0;
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 86e708a78..f851e82c4 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -33,6 +33,14 @@ enum DivAudioExportModes {
   DIV_EXPORT_MODE_MANY_CHAN
 };
 
+enum DivHaltPositions {
+  DIV_HALT_NONE=0,
+  DIV_HALT_TICK,
+  DIV_HALT_ROW,
+  DIV_HALT_PATTERN,
+  DIV_HALT_BREAKPOINT
+};
+
 struct DivChannelState {
   std::vector<DivDelayedCommand> delayed;
   int note, oldNote, pitch, portaSpeed, portaNote;
@@ -139,12 +147,14 @@ class DivEngine {
   bool repeatPattern;
   bool metronome;
   bool exporting;
+  bool halted;
   int ticks, curRow, curOrder, remainingLoops, nextSpeed, divider;
   int cycles, clockDrift;
   int changeOrd, changePos, totalSeconds, totalTicks, totalTicksR, totalCmds, lastCmds, cmdsPerSecond, globalPitch;
   unsigned char extValue;
   unsigned char speed1, speed2;
   DivStatusView view;
+  DivHaltPositions haltOn;
   DivChannelState chan[DIV_MAX_CHANS];
   DivAudioEngines audioEngine;
   DivAudioExportModes exportMode;
@@ -483,6 +493,21 @@ class DivEngine {
     // set metronome
     void setMetronome(bool enable);
 
+    // halt now
+    void halt();
+
+    // resume from halt
+    void resume();
+
+    // halt on next something
+    void haltWhen(DivHaltPositions when);
+
+    // is engine halted
+    bool isHalted();
+
+    // get register cheatsheet
+    const char** getRegisterSheet(int sys);
+
     // public render samples
     void renderSamplesP();
 
@@ -542,6 +567,7 @@ class DivEngine {
       repeatPattern(false),
       metronome(false),
       exporting(false),
+      halted(false),
       ticks(0),
       curRow(0),
       curOrder(0),
@@ -562,6 +588,7 @@ class DivEngine {
       speed1(3),
       speed2(3),
       view(DIV_STATUS_NOTHING),
+      haltOn(DIV_HALT_NONE),
       audioEngine(DIV_AUDIO_NULL),
       samp_bbInLen(0),
       samp_temp(0),
diff --git a/src/engine/platform/abstract.cpp b/src/engine/platform/abstract.cpp
index abfb843c5..369b2a059 100644
--- a/src/engine/platform/abstract.cpp
+++ b/src/engine/platform/abstract.cpp
@@ -86,6 +86,10 @@ void DivDispatch::poke(std::vector<DivRegWrite>& wlist) {
   
 }
 
+const char** DivDispatch::getRegisterSheet() {
+  return NULL;
+}
+
 int DivDispatch::init(DivEngine* p, int channels, int sugRate, unsigned int flags) {
   return 0;
 }
diff --git a/src/engine/platform/amiga.cpp b/src/engine/platform/amiga.cpp
index 83a2e9745..12ab18a5b 100644
--- a/src/engine/platform/amiga.cpp
+++ b/src/engine/platform/amiga.cpp
@@ -40,6 +40,10 @@ const char* regCheatSheetAmiga[]={
   NULL
 };
 
+const char** DivPlatformAmiga::getRegisterSheet() {
+  return regCheatSheetAmiga;
+}
+
 void DivPlatformAmiga::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   for (size_t h=start; h<start+len; h++) {
     bufL[h]=0;
diff --git a/src/engine/platform/amiga.h b/src/engine/platform/amiga.h
index 87287b9cd..475c45233 100644
--- a/src/engine/platform/amiga.h
+++ b/src/engine/platform/amiga.h
@@ -61,6 +61,7 @@ class DivPlatformAmiga: public DivDispatch {
     void notifyInsChange(int ins);
     void notifyWaveChange(int wave);
     void notifyInsDeletion(void* ins);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
 };
diff --git a/src/engine/platform/arcade.cpp b/src/engine/platform/arcade.cpp
index 174a1f43a..dd6492809 100644
--- a/src/engine/platform/arcade.cpp
+++ b/src/engine/platform/arcade.cpp
@@ -57,6 +57,10 @@ const char* regCheatSheetOPM[]={
   NULL
 };
 
+const char** DivPlatformArcade::getRegisterSheet() {
+  return regCheatSheetOPM;
+}
+
 void DivPlatformArcade::acquire_nuked(short* bufL, short* bufR, size_t start, size_t len) {
   static int o[2];
 
diff --git a/src/engine/platform/arcade.h b/src/engine/platform/arcade.h
index ca6027d46..a10933e1b 100644
--- a/src/engine/platform/arcade.h
+++ b/src/engine/platform/arcade.h
@@ -81,6 +81,7 @@ class DivPlatformArcade: public DivDispatch {
     void setYMFM(bool use);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
     ~DivPlatformArcade();
diff --git a/src/engine/platform/ay.cpp b/src/engine/platform/ay.cpp
index e2edfc5e8..b45749602 100644
--- a/src/engine/platform/ay.cpp
+++ b/src/engine/platform/ay.cpp
@@ -29,6 +29,10 @@ const char* regCheatSheetAY[]={
   NULL
 };
 
+const char** DivPlatformAY8910::getRegisterSheet() {
+  return regCheatSheetAY;
+}
+
 void DivPlatformAY8910::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   if (ayBufLen<len) {
     ayBufLen=len;
diff --git a/src/engine/platform/ay.h b/src/engine/platform/ay.h
index 12029f828..ee7aacd5d 100644
--- a/src/engine/platform/ay.h
+++ b/src/engine/platform/ay.h
@@ -67,6 +67,7 @@ class DivPlatformAY8910: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
 };
diff --git a/src/engine/platform/ay8930.cpp b/src/engine/platform/ay8930.cpp
index 02c4855c8..9bbc8084f 100644
--- a/src/engine/platform/ay8930.cpp
+++ b/src/engine/platform/ay8930.cpp
@@ -41,6 +41,10 @@ const char* regCheatSheetAY8930[]={
   NULL
 };
 
+const char** DivPlatformAY8930::getRegisterSheet() {
+  return regCheatSheetAY8930;
+}
+
 void DivPlatformAY8930::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   if (ayBufLen<len) {
     ayBufLen=len;
diff --git a/src/engine/platform/ay8930.h b/src/engine/platform/ay8930.h
index cea171d32..47e25fec4 100644
--- a/src/engine/platform/ay8930.h
+++ b/src/engine/platform/ay8930.h
@@ -60,6 +60,7 @@ class DivPlatformAY8930: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
 };
diff --git a/src/engine/platform/c64.cpp b/src/engine/platform/c64.cpp
index d7f98a2b2..a8e6f95d9 100644
--- a/src/engine/platform/c64.cpp
+++ b/src/engine/platform/c64.cpp
@@ -39,6 +39,10 @@ const char* regCheatSheetSID[]={
   NULL
 };
 
+const char** DivPlatformC64::getRegisterSheet() {
+  return regCheatSheetSID;
+}
+
 void DivPlatformC64::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   for (size_t i=start; i<start+len; i++) {
     sid.clock();
diff --git a/src/engine/platform/c64.h b/src/engine/platform/c64.h
index f61001648..b41d0f62c 100644
--- a/src/engine/platform/c64.h
+++ b/src/engine/platform/c64.h
@@ -68,6 +68,7 @@ class DivPlatformC64: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void setChipModel(bool is6581);
     void quit();
diff --git a/src/engine/platform/gb.cpp b/src/engine/platform/gb.cpp
index fc5f7d9fe..9809aa23b 100644
--- a/src/engine/platform/gb.cpp
+++ b/src/engine/platform/gb.cpp
@@ -38,6 +38,10 @@ const char* regCheatSheetGB[]={
   NULL
 };
 
+const char** DivPlatformGB::getRegisterSheet() {
+  return regCheatSheetGB;
+}
+
 void DivPlatformGB::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   for (size_t i=start; i<start+len; i++) {
     GB_advance_cycles(gb,16);
diff --git a/src/engine/platform/gb.h b/src/engine/platform/gb.h
index 5ee98eae0..76068ff03 100644
--- a/src/engine/platform/gb.h
+++ b/src/engine/platform/gb.h
@@ -53,6 +53,7 @@ class DivPlatformGB: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
     ~DivPlatformGB();
diff --git a/src/engine/platform/nes.cpp b/src/engine/platform/nes.cpp
index 8105740d0..98d3ea894 100644
--- a/src/engine/platform/nes.cpp
+++ b/src/engine/platform/nes.cpp
@@ -32,6 +32,10 @@ const char* regCheatSheetNES[]={
   NULL
 };
 
+const char** DivPlatformNES::getRegisterSheet() {
+  return regCheatSheetNES;
+}
+
 void DivPlatformNES::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   for (size_t i=start; i<start+len; i++) {
     if (dacSample!=-1) {
diff --git a/src/engine/platform/nes.h b/src/engine/platform/nes.h
index edc130ae3..58c54156a 100644
--- a/src/engine/platform/nes.h
+++ b/src/engine/platform/nes.h
@@ -56,6 +56,7 @@ class DivPlatformNES: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
     ~DivPlatformNES();
diff --git a/src/engine/platform/pce.cpp b/src/engine/platform/pce.cpp
index 175c66b00..fe246f540 100644
--- a/src/engine/platform/pce.cpp
+++ b/src/engine/platform/pce.cpp
@@ -29,6 +29,10 @@ const char* regCheatSheetPCE[]={
   NULL
 };
 
+const char** DivPlatformPCE::getRegisterSheet() {
+  return regCheatSheetPCE;
+}
+
 void DivPlatformPCE::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   for (size_t h=start; h<start+len; h++) {
     // PCM part
diff --git a/src/engine/platform/pce.h b/src/engine/platform/pce.h
index 3463abd7d..62e056be5 100644
--- a/src/engine/platform/pce.h
+++ b/src/engine/platform/pce.h
@@ -72,6 +72,7 @@ class DivPlatformPCE: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
     ~DivPlatformPCE();
diff --git a/src/engine/platform/saa.cpp b/src/engine/platform/saa.cpp
index c2cb7224c..6e23569c2 100644
--- a/src/engine/platform/saa.cpp
+++ b/src/engine/platform/saa.cpp
@@ -33,6 +33,10 @@ const char* regCheatSheetSAA[]={
   NULL
 };
 
+const char** DivPlatformSAA1099::getRegisterSheet() {
+  return regCheatSheetSAA;
+}
+
 void DivPlatformSAA1099::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   if (saaBufLen<len) {
     saaBufLen=len;
diff --git a/src/engine/platform/saa.h b/src/engine/platform/saa.h
index 98e0fe56c..d82f6fca2 100644
--- a/src/engine/platform/saa.h
+++ b/src/engine/platform/saa.h
@@ -64,6 +64,7 @@ class DivPlatformSAA1099: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
 };
diff --git a/src/engine/platform/sms.cpp b/src/engine/platform/sms.cpp
index 57f346469..e1c806770 100644
--- a/src/engine/platform/sms.cpp
+++ b/src/engine/platform/sms.cpp
@@ -11,6 +11,10 @@ const char* regCheatSheetSN[]={
   NULL
 };
 
+const char** DivPlatformSMS::getRegisterSheet() {
+  return regCheatSheetSN;
+}
+
 void DivPlatformSMS::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   sn->sound_stream_update(bufL+start,len);
 }
diff --git a/src/engine/platform/sms.h b/src/engine/platform/sms.h
index aa8725e70..5eced7ed6 100644
--- a/src/engine/platform/sms.h
+++ b/src/engine/platform/sms.h
@@ -50,6 +50,7 @@ class DivPlatformSMS: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
     ~DivPlatformSMS();
diff --git a/src/engine/platform/tia.cpp b/src/engine/platform/tia.cpp
index d3bff8e48..e29e01009 100644
--- a/src/engine/platform/tia.cpp
+++ b/src/engine/platform/tia.cpp
@@ -15,6 +15,10 @@ const char* regCheatSheetTIA[]={
   NULL
 };
 
+const char** DivPlatformTIA::getRegisterSheet() {
+  return regCheatSheetTIA;
+}
+
 void DivPlatformTIA::acquire(short* bufL, short* bufR, size_t start, size_t len) {
   tia.process(bufL+start,len);
 }
diff --git a/src/engine/platform/tia.h b/src/engine/platform/tia.h
index a0a9bf21f..b31f4b57c 100644
--- a/src/engine/platform/tia.h
+++ b/src/engine/platform/tia.h
@@ -37,6 +37,7 @@ class DivPlatformTIA: public DivDispatch {
     void notifyInsDeletion(void* ins);
     void poke(unsigned int addr, unsigned short val);
     void poke(std::vector<DivRegWrite>& wlist);
+    const char** getRegisterSheet();
     int init(DivEngine* parent, int channels, int sugRate, unsigned int flags);
     void quit();
 };
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index da325ff69..ffc1e4e0d 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -791,8 +791,10 @@ void DivEngine::nextRow() {
       }
       changeOrd=-1;
     }
+    if (haltOn==DIV_HALT_PATTERN) halted=true;
   } else if (++curRow>=song.patLen) {
     nextOrder();
+    if (haltOn==DIV_HALT_PATTERN) halted=true;
   }
 
   if (speedAB) {
@@ -813,6 +815,8 @@ void DivEngine::nextRow() {
       }
     }
   }
+
+  if (haltOn==DIV_HALT_ROW) halted=true;
 }
 
 bool DivEngine::nextTick(bool noAccum) {
@@ -967,6 +971,8 @@ bool DivEngine::nextTick(bool noAccum) {
     if (consoleMode) fprintf(stderr,"\x1b[2K> %d:%.2d:%.2d.%.2d  %.2x/%.2x:%.3d/%.3d  %4dcmd/s\x1b[G",totalSeconds/3600,(totalSeconds/60)%60,totalSeconds%60,totalTicks/10000,curOrder,song.ordersLen,curRow,song.patLen,cmdsPerSecond);
   }
 
+  if (haltOn==DIV_HALT_TICK) halted=true;
+
   return ret;
 }
 
@@ -1076,6 +1082,8 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
   int attempts=0;
   int runLeftG=size<<MASTER_CLOCK_PREC;
   while (++attempts<100) {
+    // 0. check if we've halted
+    if (halted) break;
     // 1. check whether we are done with all buffers
     if (runLeftG<=0) break;
 
@@ -1124,6 +1132,12 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
       }
     }
   }
+
+  if (out==NULL || halted) {
+    isBusy.unlock();
+    return;
+  }
+
   logD("attempts: %d\n",attempts);
   if (attempts>=100) {
     logE("hang detected! stopping! at %d seconds %d micro\n",totalSeconds,totalTicks);
@@ -1137,11 +1151,6 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
     disCont[i].fillBuf(runtotal[i],size);
   }
 
-  if (out==NULL) {
-    isBusy.unlock();
-    return;
-  }
-
   for (int i=0; i<song.systemLen; i++) {
     float volL=((float)song.systemVol[i]/64.0f)*((float)MIN(127,127-(int)song.systemPan[i])/127.0f);
     float volR=((float)song.systemVol[i]/64.0f)*((float)MIN(127,127+(int)song.systemPan[i])/127.0f);
diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index f28b72c0e..d089d6dac 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -3229,15 +3229,19 @@ void FurnaceGUI::drawDebug() {
   if (ImGui::Begin("Debug",&debugOpen,ImGuiWindowFlags_NoDocking)) {
     ImGui::Text("NOTE: use with caution.");
     if (ImGui::TreeNode("Debug Controls")) {
-      ImGui::Button("Pause");
+      if (e->isHalted()) {
+        if (ImGui::Button("Resume")) e->resume();
+      } else {
+        if (ImGui::Button("Pause")) e->halt();
+      }
       ImGui::SameLine();
-      ImGui::Button("Frame Advance");
+      if (ImGui::Button("Frame Advance")) e->haltWhen(DIV_HALT_TICK);
       ImGui::SameLine();
-      ImGui::Button("Row Advance");
+      if (ImGui::Button("Row Advance")) e->haltWhen(DIV_HALT_ROW);
       ImGui::SameLine();
-      ImGui::Button("Pattern Advance");
+      if (ImGui::Button("Pattern Advance")) e->haltWhen(DIV_HALT_PATTERN);
 
-      ImGui::Button("Panic");
+      if (ImGui::Button("Panic")) e->syncReset();
       ImGui::SameLine();
       if (ImGui::Button("Abort")) {
         abort();
@@ -3389,6 +3393,29 @@ void FurnaceGUI::drawDebug() {
       if (ImGui::Button("Add")) {
         pgProgram.push_back(DivRegWrite(pgAddr,pgVal));
       }
+      if (ImGui::TreeNode("Register Cheatsheet")) {
+        const char** sheet=e->getRegisterSheet(pgSys);
+        if (sheet==NULL) {
+          ImGui::Text("no cheatsheet available for this system.");
+        } else {
+          if (ImGui::BeginTable("RegisterSheet",2,ImGuiTableFlags_SizingFixedSame)) {
+            ImGui::TableNextRow();
+            ImGui::TableNextColumn();
+            ImGui::Text("Name");
+            ImGui::TableNextColumn();
+            ImGui::Text("Address");
+            for (int i=0; sheet[i]!=NULL; i+=2) {
+              ImGui::TableNextRow();
+              ImGui::TableNextColumn();
+              ImGui::Text("%s",sheet[i]);
+              ImGui::TableNextColumn();
+              ImGui::Text("$%s",sheet[i+1]);
+            }
+            ImGui::EndTable();
+          }
+        }
+        ImGui::TreePop();
+      }
       ImGui::TreePop();
     }
     if (ImGui::TreeNode("Settings")) {