Tweaks in preparation for web module

core/bus.c

@@ -95,16 +95,16 @@ static int32_t busReadMisc(VB *sim, uint8_t address, int type) {
 
     /* Access by register */
     switch (address >> 2 & 15) {
-        case 0x00>>2: break; /* CCR */
-        case 0x04>>2: break; /* CCSR */
-        case 0x08>>2: break; /* CDTR */
-        case 0x0C>>2: break; /* CDRR */
+        case 0x00>>2: return extReadCCR(sim);                      /* CCR */
+        case 0x04>>2: return extReadCCSR(sim);                     /* CCSR */
+        case 0x08>>2: return sim->ext.cdtr;                        /* CDTR */
+        case 0x0C>>2: return sim->ext.cdrr;                        /* CDRR */
         case 0x10>>2: return sim->pad.sdlr;                        /* SDLR */
         case 0x14>>2: return sim->pad.sdhr;                        /* SDHR */
         case 0x18>>2: return sim->tmr.counter      & 0xFF;         /* TLR */
         case 0x1C>>2: return sim->tmr.counter >> 8 & 0xFF;         /* THR */
         case 0x20>>2: return tmrReadControl(sim);                  /* TCR */
-        case 0x24>>2: return sim->wcr;                     /* WCR */
+        case 0x24>>2: return sim->wcr.exp1w << 1 | sim->wcr.rom1w; /* WCR */
         case 0x28>>2: return padReadControl(sim);                  /* SCR */
     }
 
@@ -123,15 +123,16 @@ static void busWriteMisc(VB *sim, uint8_t address, int type, int32_t value) {
 
     /* Access by register */
     switch (address >> 2 & 15) {
-        case 0x00>>2: break; /* CCR */
-        case 0x04>>2: break; /* CCSR */
-        case 0x08>>2: break; /* CDTR */
-        case 0x0C>>2: break; /* CDRR */
+        case 0x00>>2: extWriteCCR (sim, value);    break; /* CCR */
+        case 0x04>>2: extWriteCCSR(sim, value);    break; /* CCSR */
+        case 0x08>>2: sim->ext.cdtr = value;       break; /* CDTR */
         case 0x18>>2: tmrWriteLow    (sim, value); break; /* TLR */
         case 0x1C>>2: tmrWriteHigh   (sim, value); break; /* THR */
         case 0x20>>2: tmrWriteControl(sim, value); break; /* TCR */
-        case 0x24>>2: sim->wcr = value & 3;        break; /* WCR */
         case 0x28>>2: padWriteControl(sim, value); break; /* SCR */
+        case 0x24>>2:                                     /* WCR */
+            sim->wcr.exp1w = value >> 1 & 1;
+            sim->wcr.rom1w = value      & 1;
     }
 
 }

core/ext.c

@@ -0,0 +1,164 @@
+/* This file is included into vb.c and cannot be compiled on its own. */
+#ifdef VBAPI
+
+
+
+/***************************** Callback Handlers *****************************/
+
+/* Prepare to handle an exception */
+#ifndef VB_DIRECT_LINK
+    #define VB_ON_LINK sim1->onLink
+#else
+    extern int VB_DIRECT_LINK(VB *, VB *, uint8_t *, uint8_t *);
+    #define VB_ON_LINK VB_DIRECT_LINK
+#endif
+static int extOnLink(VB *sim1, VB *sim2, uint8_t *value1, uint8_t *value2) {
+    return sim1->onLink != NULL && VB_ON_LINK(sim1, sim2, value1, value2);
+}
+#undef VB_ON_LINK
+
+
+
+/***************************** Library Functions *****************************/
+
+/* Process component */
+static int extEmulate(VB *sim, uint32_t clocks) {
+    VB     *peer;      /* Communication peer */
+    VB     *sims[2];   /* Communication peers */
+    uint8_t values[2]; /* Transmission values */
+    int     x;         /* Iterator */
+
+    /* Communication will not occur */
+    if (!sim->ext.c_stat || sim->ext.c_clk_sel)
+        return 0;
+
+    /* Communication completes after time to process */
+    if (sim->ext.clocks > clocks) {
+        sim->ext.clocks -= clocks;
+        return 0;
+    }
+
+    /* Exchange transmission data */
+    sims  [0] = sim;
+    sims  [1] = sim->peer;
+    values[0] = sim->ext.cdtr;
+    values[1] = sim->peer == NULL ? 0 : sim->peer->ext.cdtr;
+    if (extOnLink(sim, sim->peer, &values[0], &values[1]))
+        return 1;
+
+    /* Update state */
+    for (x = 0; x < 2; x++) {
+        sim  = sims[x];
+        peer = sims[x ^ 1];
+        if (sim  == NULL)
+            break;
+        if (peer == NULL)
+            peer = sim;
+
+        /* Registers */
+        sim->ext.cdrr    = values[x ^ 1];
+        sim->ext.c_irq  |= !sim->ext.c_int_inh;
+        sim->ext.c_stat  = 0;
+        sim->ext.cc_rd   = sim->ext.cc_wr  & peer->ext.cc_wr;
+        sim->ext.cc_smp  = sim->ext.cc_sig & peer->ext.cc_sig & sim->ext.cc_rd;
+        sim->ext.cc_irq |= !sim->ext.cc_int_inh &&
+            sim->ext.cc_smp == sim->ext.cc_int_lev;
+
+        /* Interrupt */
+        if (sim->ext.c_irq | sim->ext.cc_irq)
+            sim->cpu.irq |= 0x0008;
+    }
+    return 0;
+}
+
+/* Read a value from CCR */
+static int32_t extReadCCR(VB *sim) {
+    return 0x6D |
+        sim->ext.c_int_inh << 7 |
+        sim->ext.c_clk_sel << 4 |
+        sim->ext.c_stat    << 1
+    ;
+}
+
+/* Read a value from CCSR */
+static int32_t extReadCCSR(VB *sim) {
+    sim->ext.cc_rd = sim->ext.cc_wr &
+        (sim->peer == NULL ? 1 : sim->peer->ext.cc_wr);
+    return 0x60 |
+        sim->ext.cc_int_inh << 7 |
+        sim->ext.cc_int_lev << 4 |
+        sim->ext.cc_sig     << 3 |
+        sim->ext.cc_smp     << 2 |
+        sim->ext.cc_wr      << 1 |
+        sim->ext.cc_rd
+    ;
+}
+
+/* Simulate a hardware reset */
+static void extReset(VB *sim) {
+
+    /* Normal */
+    sim->ext.c_clk_sel  = 0;
+    sim->ext.c_int_inh  = 0;
+    sim->ext.c_stat     = 0;
+    sim->ext.cc_int_inh = 1;
+    sim->ext.cc_int_lev = 1;
+    sim->ext.cc_sig     = 1;
+    sim->ext.cc_wr      = 1;
+    sim->ext.cdrr       = 0x00;
+    sim->ext.cdtr       = 0x00;
+
+    /* Other */
+    sim->ext.c_irq  = 0;
+    sim->ext.cc_irq = 0;
+}
+
+/* Determine how many clocks are guaranteed to process */
+static uint32_t extUntil(VB *sim, uint32_t clocks) {
+    return !sim->ext.c_stat || sim->ext.c_clk_sel || clocks < sim->ext.clocks ?
+        clocks : sim->ext.clocks;
+}
+
+/* Write a value to CCR */
+static void extWriteCCR(VB *sim, uint8_t value) {
+
+    /* Configure state */
+    sim->ext.c_int_inh = value >> 7 & 1;
+    sim->ext.c_clk_sel = value >> 4 & 1;
+
+    /* Acknowledge interrupt */
+    if (sim->ext.c_int_inh) {
+        sim->ext.c_irq = 0;
+        if (!sim->ext.cc_irq)
+            sim->cpu.irq &= ~0x0008;
+    }
+
+    /* Do not initiate a communication */
+    if (sim->ext.c_stat || (value & 0x04) == 0) /* C-Start */
+        return;
+
+    /* Initiate a communication */
+    sim->ext.c_stat = 1;
+    sim->ext.clocks = 3200; /* 160us */
+}
+
+/* Write a value to CCSR */
+static void extWriteCCSR(VB *sim, uint8_t value) {
+
+    /* Configure state */
+    sim->ext.cc_int_inh = value >> 7 & 1;
+    sim->ext.cc_int_lev = value >> 4 & 1;
+    sim->ext.cc_sig     = value >> 3 & 1;
+    sim->ext.cc_wr      = value >> 1 & 1;
+
+    /* Acknowledge interrupt */
+    if (!sim->ext.cc_int_inh)
+        return;
+    sim->ext.cc_irq = 0;
+    if (!sim->ext.c_irq)
+        sim->cpu.irq &= ~0x0008;
+}
+
+
+
+#endif /* VBAPI */

core/game-pad.c

@@ -9,12 +9,12 @@
 static void padEmulate(VB *sim, uint32_t clocks) {
 
     /* No hardware read in progress */
-    if (sim->pad.si_stat == 0)
+    if (!sim->pad.si_stat)
         return;
 
     /* Hardware read completes after time to process */
-    if (sim->pad.si_stat > clocks) {
-        sim->pad.si_stat -= clocks;
+    if (sim->pad.clocks > clocks) {
+        sim->pad.clocks -= clocks;
         return;
     }
 
@@ -38,7 +38,7 @@ static int32_t padReadControl(VB *sim) {
         sim->pad.k_int_inh << 7 |
         sim->pad.para_si   << 5 |
         sim->pad.soft_ck   << 4 |
-        !!sim->pad.si_stat << 1 |
+        sim->pad.si_stat   << 1 |
         sim->pad.s_abt_dis
     ;
 }
@@ -78,7 +78,8 @@ static void padWriteControl(VB *sim, uint8_t value) {
         sim->pad.si_stat == 0 && /* No hardware read underway */
         !sim->pad.s_abt_dis      /* Hardware reads enabled */
     ) {
-        sim->pad.si_stat = 10240; /* 512us */
+        sim->pad.clocks  = 10240; /* 512us */
+        sim->pad.si_stat = 1;
         sim->pad.step    = 0;     /* Abort software read */
     }
 
@@ -86,7 +87,7 @@ static void padWriteControl(VB *sim, uint8_t value) {
     sim->pad.para_si = value >> 5 & 1;
     if (
         sim->pad.para_si &&
-        sim->pad.si_stat == 0 /* No hardware read underway */
+        !sim->pad.si_stat /* No hardware read underway */
     ) sim->pad.step = 32;
 
     /* Signal a bit for a software read */
@@ -107,8 +108,8 @@ static void padWriteControl(VB *sim, uint8_t value) {
 
 /* Determine how many clocks are guaranteed to process */
 static uint32_t padUntil(VB *sim, uint32_t clocks) {
-    return sim->pad.si_stat != 0 && sim->pad.si_stat < clocks ?
-        sim->pad.si_stat : clocks;
+    return sim->pad.si_stat && sim->pad.clocks < clocks ?
+        sim->pad.clocks : clocks;
 }
 
 

core/pseudo-halt.c

@@ -142,6 +142,7 @@ static uint32_t phDPSTTS(VB *sim) {
         case 3: /* 8ms - L*BSY falling edge */
         case 6: /* 13ms-18ms - Display right frame buffer */
         case 7: /* 18ms - R*BSY falling edge */
+        case 8: /* 20ms - Display interval complete */
             return sim->vip.dp.until;
     }
     /* case 1: 3ms - L*BSY rising edge */

core/vb.c

@@ -146,6 +146,28 @@ struct VB {
         int      step;      /* Operation sub-task ID */
     } cpu;
 
+    /* Communication port */
+    struct {
+
+        /* Register state */
+        uint8_t c_clk_sel;  /* Transmission clock source */
+        uint8_t c_int_inh;  /* Interrupt acknowledge/disable */
+        uint8_t c_stat;     /* Communication is underway */
+        uint8_t cc_int_inh; /* Interrupt acknowledge/disable */
+        uint8_t cc_int_lev; /* Interrupt condition */
+        uint8_t cc_rd;      /* Manual read */
+        uint8_t cc_sig;     /* Automatic write */
+        uint8_t cc_smp;     /* Automatic read */
+        uint8_t cc_wr;      /* Manual write */
+        uint8_t cdrr;       /* Data received */
+        uint8_t cdtr;       /* Data to transmit */
+
+        /* Other state */
+        int8_t   c_irq;  /* COM interrupt request */
+        int8_t   cc_irq; /* COMCNT interrupt request */
+        uint32_t clocks; /* Master clocks to wait */
+    } ext;
+
     /* Game pad */
     struct {
 
@@ -159,6 +181,7 @@ struct VB {
         uint8_t  soft_ck;   /* Controller communication signal */
 
         /* Other state */
+        uint32_t clocks; /* Master clocks to wait */
         uint16_t keys;   /* Next input bits */
         int      step;   /* Software read processing phase */
     } pad;
@@ -296,9 +319,10 @@ struct VB {
         struct {
             float    i1[2];    /* Previous analog input sample */
             float    o1[2];    /* Previous analog output sample */
-            uint32_t capacity; /* Number of audio frames in samples */
-            uint32_t offset;   /* Position in output buffer */
-            int16_t *samples;  /* Output memory */
+            unsigned capacity; /* Number of audio frames in output buffer */
+            unsigned offset;   /* Position in output buffer */
+            void    *samples;  /* Output buffer */
+            int      type;     /* Output data type */
         } out;
 
         /* Memory */
@@ -310,6 +334,12 @@ struct VB {
         int      sample; /* Output sample index, period 417 */
     } vsu;
 
+    /* Wait controller */
+    struct {
+        uint8_t exp1w; /* Cartridge expansion 1-wait */
+        uint8_t rom1w; /* Cartridge ROM 1-wait */
+    } wcr;
+
     /* Pseudo-halt */
     struct {
         uint32_t address;   /* Monitor address */
@@ -335,7 +365,6 @@ struct VB {
     } ph;
 
     /* Other state */
-    uint8_t wcr;           /* Wait controller state */
     uint8_t wram[0x10000]; /* System RAM */
 
     /* Application data */
@@ -343,9 +372,11 @@ struct VB {
     vbOnExecute   onExecute;   /* CPU instruction execute */
     vbOnFetch     onFetch;     /* CPU instruction fetch */
     vbOnFrame     onFrame;     /* VIP frame ready */
+    vbOnLink      onLink;      /* Communication transfer */
     vbOnRead      onRead;      /* CPU instruction read */
     vbOnSamples   onSamples;   /* VSU samples full */
     vbOnWrite     onWrite;     /* CPU instruction write */
+    VB           *peer;        /* Communication peer */
     void         *tag;         /* User data */
 };
 
@@ -368,6 +399,7 @@ static int32_t SignExtend(int32_t value, int32_t bits) {
 
 /******************************** Sub-Modules ********************************/
 
+#include "ext.c"
 #include "game-pad.c"
 #include "timer.c"
 #include "bus.c"
@@ -391,7 +423,8 @@ static int sysEmulate(VB *sim, uint32_t clocks) {
     ;
 
     /* Process all components */
-    if (!never) ret  = cpuEmulate(sim, clocks);
+    if (!never){ret  = cpuEmulate(sim, clocks);}
+                ret |= extEmulate(sim, clocks);
                        padEmulate(sim, clocks);
                        tmrEmulate(sim, clocks);
                        vsuEmulate(sim, clocks);
@@ -403,6 +436,7 @@ static int sysEmulate(VB *sim, uint32_t clocks) {
 /* Determine how many clocks are guaranteed to process */
 static uint32_t sysUntil(VB *sim, uint32_t clocks) {
     clocks = cpuUntil(sim, clocks);
+    clocks = extUntil(sim, clocks);
     clocks = padUntil(sim, clocks);
     clocks = tmrUntil(sim, clocks);
     clocks = vipUntil(sim, clocks);
@@ -428,19 +462,23 @@ VBAPI int vbEmulate(VB *sim, uint32_t *clocks) {
 }
 
 /* Process multiple simulations */
-VBAPI int vbEmulateEx(VB **sims, int count, uint32_t *clocks) {
+VBAPI int vbEmulateEx(VB **sims, unsigned count, uint32_t *clocks) {
     int      brk;   /* A callback requested a break */
     uint32_t until; /* Clocks guaranteed to process */
-    int      x;     /* Iterator */
+    unsigned x;     /* Iterator */
+
+    /* Process one simulation */
+    if (count == 1)
+        return vbEmulate(sims[0], clocks);
+
+    /* Process multiple simulations */
     while (*clocks != 0) {
         until = *clocks;
-        for (x = count - 1; x >= 0; x--)
-            until = sysUntil(sims[x], until);
-
+        for (x = count; x > 0; x--)
+            until = sysUntil(sims[x - 1], until);
         brk = 0;
-        for (x = count - 1; x >= 0; x--)
-            brk |= sysEmulate(sims[x], until);
-
+        for (x = count; x > 0; x--)
+            brk |= sysEmulate(sims[x - 1], until);
         *clocks -= until;
         if (brk)
             return brk; /* TODO: return 1 */
@@ -487,6 +525,11 @@ VBAPI uint16_t vbGetKeys(VB *sim) {
     return sim->pad.keys;
 }
 
+/* Retrieve the current link callback handler */
+VBAPI vbOnLink vbGetLinkCallback(VB *sim) {
+    return sim->onLink;
+}
+
 /* Retrieve a core option value */
 VBAPI int vbGetOption(VB *sim, int key) {
     switch (key) {
@@ -495,6 +538,11 @@ VBAPI int vbGetOption(VB *sim, int key) {
     return 0;
 }
 
+/* Retrieve the communication peer */
+VBAPI VB* vbGetPeer(VB *sim) {
+    return sim->peer;
+}
+
 /* Retrieve the most recent frame image pixels */
 VBAPI void vbGetPixels(VB *sim, void *left, int leftStrideX, int leftStrideY,
     void *right, int rightStrideX, int rightStrideY) {
@@ -541,7 +589,7 @@ VBAPI uint32_t vbGetProgramCounter(VB *sim) {
 }
 
 /* Retrieve the value in a program register */
-VBAPI int32_t vbGetProgramRegister(VB *sim, int index) {
+VBAPI int32_t vbGetProgramRegister(VB *sim, unsigned index) {
     return index < 1 || index > 31 ? 0 : sim->cpu.program[index];
 }
 
@@ -551,13 +599,18 @@ VBAPI vbOnRead vbGetReadCallback(VB *sim) {
 }
 
 /* Retrieve the audio samples buffer */
-VBAPI void* vbGetSamples(VB *sim, uint32_t *capacity, uint32_t *position) {
+VBAPI void* vbGetSamples(VB *sim, int *type,
+    unsigned *capacity, unsigned *position) {
     if (sim->vsu.out.samples == NULL) {
+        if (type     != NULL)
+            *type     = 0;
         if (capacity != NULL)
             *capacity = 0;
         if (position != NULL)
             *position = 0;
     } else {
+        if (type     != NULL)
+            *type     = sim->vsu.out.type;
         if (capacity != NULL)
             *capacity = sim->vsu.out.capacity;
         if (position != NULL)
@@ -572,8 +625,8 @@ VBAPI vbOnSamples vbGetSamplesCallback(VB *sim) {
 }
 
 /* Retrieve the value in a system register */
-VBAPI uint32_t vbGetSystemRegister(VB *sim, int index) {
-    return index < 0 || index > 31 ? 0 : cpuGetSystemRegister(sim, index);
+VBAPI uint32_t vbGetSystemRegister(VB *sim, unsigned index) {
+    return index > 31 ? 0 : cpuGetSystemRegister(sim, index);
 }
 
 /* Retrieve a simulation's userdata pointer */
@@ -594,9 +647,11 @@ VBAPI VB* vbInit(VB *sim) {
     sim->onExecute       = NULL;
     sim->onFetch         = NULL;
     sim->onFrame         = NULL;
+    sim->onLink          = NULL;
     sim->onRead          = NULL;
     sim->onSamples       = NULL;
     sim->onWrite         = NULL;
+    sim->peer            = NULL;
     sim->ph.enabled      = 0;
     vbReset(sim);
     return sim;
@@ -616,7 +671,8 @@ VBAPI VB* vbReset(VB *sim) {
     int x; /* Iterator */
 
     /* Wait controller */
-    sim->wcr = 0x00;
+    sim->wcr.exp1w = 0;
+    sim->wcr.rom1w = 0;
 
     /* WRAM (the hardware does not do this) */
     for (x = 0; x < 0x10000; x++)
@@ -624,6 +680,7 @@ VBAPI VB* vbReset(VB *sim) {
 
     /* Components */
     cpuReset(sim);
+    extReset(sim);
     padReset(sim);
     tmrReset(sim);
     vipReset(sim);
@@ -689,6 +746,13 @@ VBAPI uint16_t vbSetKeys(VB *sim, uint16_t keys) {
     return sim->pad.keys = keys;
 }
 
+/* Specify a new link callback handler */
+VBAPI vbOnLink vbSetLinkCallback(VB *sim, vbOnLink callback) {
+    vbOnLink prev = sim->onLink;
+    sim->onLink = callback;
+    return prev;
+}
+
 /* Specify a new core option value */
 VBAPI int vbSetOption(VB *sim, int key, int value) {
     switch (key) {
@@ -706,6 +770,18 @@ VBAPI int vbSetOption(VB *sim, int key, int value) {
     return value;
 }
 
+/* Specify a new communication peer */
+VBAPI void vbSetPeer(VB *sim, VB *peer) {
+    if (sim->peer == peer)
+        return;
+    sim->peer = peer;
+    if (peer == NULL)
+        return;
+    if (peer->peer != NULL)
+        peer->peer->peer = NULL;
+    peer->peer = sim;
+}
+
 /* Specify a new value for the program counter */
 VBAPI uint32_t vbSetProgramCounter(VB *sim, uint32_t value) {
     sim->cpu.operation = CPU_FETCH;
@@ -715,7 +791,7 @@ VBAPI uint32_t vbSetProgramCounter(VB *sim, uint32_t value) {
 }
 
 /* Specify a new value for a program register */
-VBAPI int32_t vbSetProgramRegister(VB *sim, int index, int32_t value) {
+VBAPI int32_t vbSetProgramRegister(VB *sim, unsigned index, int32_t value) {
     return index < 1 || index > 31 ? 0 : (sim->cpu.program[index] = value);
 }
 
@@ -727,12 +803,14 @@ VBAPI vbOnRead vbSetReadCallback(VB *sim, vbOnRead callback) {
 }
 
 /* Specify a new audio samples buffer */
-VBAPI int vbSetSamples(VB *sim, void *samples, uint32_t capacity) {
-    if (samples != NULL && (capacity == 0 || capacity > 0x40000000))
+VBAPI int vbSetSamples(VB *sim, void *samples, int type, unsigned capacity) {
+    if (samples != NULL &&
+        (capacity == 0 || (type != VB_S16 && type != VB_F32)))
         return 1;
-    sim->vsu.out.capacity = samples == NULL ? 0 : capacity;
+    sim->vsu.out.capacity = capacity;
     sim->vsu.out.offset   = 0;
     sim->vsu.out.samples  = samples;
+    sim->vsu.out.type     = type;
     return 0;
 }
 
@@ -744,9 +822,8 @@ VBAPI vbOnSamples vbSetSamplesCallback(VB *sim, vbOnSamples callback) {
 }
 
 /* Specify a new value for a system register */
-VBAPI uint32_t vbSetSystemRegister(VB *sim, int index, uint32_t value) {
-    return index < 0 || index > 31 ? 0 :
-        cpuSetSystemRegister(sim, index, value, 1);
+VBAPI uint32_t vbSetSystemRegister(VB *sim, unsigned index, uint32_t value) {
+    return index > 31 ? 0 : cpuSetSystemRegister(sim, index, value, 1);
 }
 
 /* Specify a new write callback handler */

core/vb.h

@@ -22,6 +22,7 @@ extern "C" {
   VB_DIRECT_EXECUTE
   VB_DIRECT_FETCH
   VB_DIRECT_FRAME
+  VB_DIRECT_LINK
   VB_DIRECT_READ
   VB_DIRECT_SAMPLES
   VB_DIRECT_WRITE
@@ -78,6 +79,7 @@ extern "C" {
 #define VB_S16 2
 #define VB_U16 3
 #define VB_S32 4
+#define VB_F32 5
 
 /* Option keys */
 #define VB_PSEUDO_HALT 0
@@ -94,6 +96,7 @@ typedef int  (*vbOnException)(VB *sim, uint16_t *cause);
 typedef int  (*vbOnExecute  )(VB *sim, uint32_t address, const uint16_t *code, int length);
 typedef int  (*vbOnFetch    )(VB *sim, int fetch, uint32_t address, int32_t *value, uint32_t *cycles);
 typedef int  (*vbOnFrame    )(VB *sim);
+typedef int  (*vbOnLink     )(VB *sim1, VB *sim2, uint8_t *value1, uint8_t *value2);
 typedef int  (*vbOnRead     )(VB *sim, uint32_t address, int type, int32_t *value, uint32_t *cycles);
 typedef void (*vbOnSamples  )(VB *sim, int16_t *buffer, uint32_t capacity);
 typedef int  (*vbOnWrite    )(VB *sim, uint32_t address, int type, int32_t *value, uint32_t *cycles, int *cancel);
@@ -104,7 +107,7 @@ typedef int  (*vbOnWrite    )(VB *sim, uint32_t address, int type, int32_t *valu
 /******************************* API Commands ********************************/
 
 VBAPI int           vbEmulate             (VB *sim, uint32_t *clocks);
-VBAPI int           vbEmulateEx           (VB **sims, int count, uint32_t *clocks);
+VBAPI int           vbEmulateEx           (VB **sims, unsigned count, uint32_t *clocks);
 VBAPI void*         vbGetCallback         (VB *sim, int id);
 VBAPI void*         vbGetCartRAM          (VB *sim, uint32_t *size);
 VBAPI void*         vbGetCartROM          (VB *sim, uint32_t *size);
@@ -113,14 +116,16 @@ VBAPI vbOnExecute   vbGetExecuteCallback  (VB *sim);
 VBAPI vbOnFetch     vbGetFetchCallback    (VB *sim);
 VBAPI vbOnFrame     vbGetFrameCallback    (VB *sim);
 VBAPI uint16_t      vbGetKeys             (VB *sim);
+VBAPI vbOnLink      vbGetLinkCallback     (VB *sim);
 VBAPI int           vbGetOption           (VB *sim, int key);
+VBAPI VB*           vbGetPeer             (VB *sim);
 VBAPI void          vbGetPixels           (VB *sim, void *left, int leftStrideX, int leftStrideY, void *right, int rightStrideX, int rightStrideY);
 VBAPI uint32_t      vbGetProgramCounter   (VB *sim);
-VBAPI int32_t       vbGetProgramRegister  (VB *sim, int index);
+VBAPI int32_t       vbGetProgramRegister  (VB *sim, unsigned index);
 VBAPI vbOnRead      vbGetReadCallback     (VB *sim);
-VBAPI void*         vbGetSamples          (VB *sim, uint32_t *capacity, uint32_t *position);
+VBAPI void*         vbGetSamples          (VB *sim, int *type, unsigned *capacity, unsigned *position);
 VBAPI vbOnSamples   vbGetSamplesCallback  (VB *sim);
-VBAPI uint32_t      vbGetSystemRegister   (VB *sim, int index);
+VBAPI uint32_t      vbGetSystemRegister   (VB *sim, unsigned index);
 VBAPI void*         vbGetUserData         (VB *sim);
 VBAPI vbOnWrite     vbGetWriteCallback    (VB *sim);
 VBAPI VB*           vbInit                (VB *sim);
@@ -132,14 +137,16 @@ VBAPI vbOnException vbSetExceptionCallback(VB *sim, vbOnException callback);
 VBAPI vbOnExecute   vbSetExecuteCallback  (VB *sim, vbOnExecute callback);
 VBAPI vbOnFetch     vbSetFetchCallback    (VB *sim, vbOnFetch callback);
 VBAPI vbOnFrame     vbSetFrameCallback    (VB *sim, vbOnFrame callback);
+VBAPI vbOnLink      vbSetLinkCallback     (VB *sim, vbOnLink callback);
 VBAPI uint16_t      vbSetKeys             (VB *sim, uint16_t keys);
 VBAPI int           vbSetOption           (VB *sim, int key, int value);
+VBAPI void          vbSetPeer             (VB *sim, VB *peer);
 VBAPI uint32_t      vbSetProgramCounter   (VB *sim, uint32_t value);
-VBAPI int32_t       vbSetProgramRegister  (VB *sim, int index, int32_t value);
+VBAPI int32_t       vbSetProgramRegister  (VB *sim, unsigned index, int32_t value);
 VBAPI vbOnRead      vbSetReadCallback     (VB *sim, vbOnRead callback);
-VBAPI int           vbSetSamples          (VB *sim, void *samples, uint32_t capacity);
+VBAPI int           vbSetSamples          (VB *sim, void *samples, int type, unsigned capacity);
 VBAPI vbOnSamples   vbSetSamplesCallback  (VB *sim, vbOnSamples callback);
-VBAPI uint32_t      vbSetSystemRegister   (VB *sim, int index, uint32_t value);
+VBAPI uint32_t      vbSetSystemRegister   (VB *sim, unsigned index, uint32_t value);
 VBAPI void*         vbSetUserData         (VB *sim, void *tag);
 VBAPI vbOnWrite     vbSetWriteCallback    (VB *sim, vbOnWrite callback);
 VBAPI size_t        vbSizeOf              ();

core/vip.c

@@ -54,6 +54,32 @@ static const uint8_t BRIGHT8[] = {
 
 
 
+/*********************************** Types ***********************************/
+
+/* World attribtues per eye */
+typedef struct {
+    int32_t bp;          /* BG source parallax */
+    int32_t left, right; /* Window bounds */
+    int32_t wx;          /* World horizontal position */
+} EyeAttribs;
+
+/* Parsed world attributes */
+typedef struct {
+    int32_t  base;        /* Base BG map index */
+    uint8_t *bg;          /* Background template */
+    int32_t  bgm;         /* World type */
+    int32_t  bgw, bgh;    /* Background dimension masks */
+    int32_t  bottom, top; /* Window bounds */
+    int32_t  gx, gp, gy;  /* World screen position */
+    int32_t  mx, mp, my;  /* Background scroll */
+    uint8_t *over;        /* Overplane character */
+    uint32_t params;      /* Line parameters address */
+    int32_t  scx, scy;    /* Background dimensions */
+    int32_t  w, h;        /* Window size */
+} WorldAttribs;
+
+
+
 /***************************** Module Functions ******************************/
 
 /* Retrieve a pointer to character data in host memory */
@@ -579,14 +605,18 @@ static int vipEmulateDisplay(VB *sim, uint32_t clocks) {
                 }
                 sim->vip.dp.clocks  = vipClocksMs(2);
                 sim->vip.dp.enabled = 0;
-                sim->vip.dp.step    = 0;
+                sim->vip.dp.step    = 8;
                 sim->vip.dp.until   = vipClocksMs(2);
-                if (vipOnFrame(sim))
-                    return 1;
                 break;
 
             /* 18ms-20ms - Idle */
 
+            case 8: /* 20ms - Display interval complete */
+                sim->vip.dp.step = 0;
+                if (vipOnFrame(sim))
+                    return 1;
+                break;
+
         }
     }
 
@@ -597,6 +627,89 @@ static int vipEmulateDisplay(VB *sim, uint32_t clocks) {
 
 /****************************** Pixel Processor ******************************/
 
+/* Parse eye attributes and test window bounds */
+static int vipParseEye(WorldAttribs *wttr, EyeAttribs *ettr, int eye) {
+
+    /* Validate the world isn't right of frame */
+    ettr->wx = wttr->gx - (eye == 0 ? wttr->gp : -wttr->gp);
+    if (ettr->wx > 383)
+        return 1;
+    ettr->left = ettr->wx < 0 ? 0 : ettr->wx;
+
+    /* Validate the world isn't left of frame */
+    ettr->right = ettr->wx + wttr->w - 1;
+    if (ettr->right < 0)
+        return 1;
+    if (ettr->right > 383)
+        ettr->right = 383;
+
+    /* BG source parallax */
+    if (wttr->bgm != 2)
+        ettr->bp = eye == 0 ? -wttr->mp : wttr->mp;
+
+    return 0;
+}
+
+/* Parse world attributes and test window bounds */
+static int vipParseWorld(VB*sim,uint8_t*world,uint16_t bits,WorldAttribs*attr){
+    int32_t z; /* Scratch */
+
+    /* Validate the world isn't below the frame */
+    attr->gy = busReadBuffer(world + 6, VB_S16);
+    if (attr->gy > 223)
+        return 1;
+
+    /* Validate the world isn't above the frame, and height is positive */
+    attr->bgm = bits >> 12 & 3;
+    attr->h   = busReadBuffer(world + 16, VB_S16) + 1;
+    z         = attr->bgm == 2 ? 0 : 8;
+    if (attr->h < z)
+        attr->h = z;
+    if (attr->h == 0)
+        return 1;
+    attr->bottom = attr->gy + attr->h - 1;
+    attr->top    = (int32_t) sim->vip.xp.sbcount << 3;
+    if (attr->bottom < attr->top)
+        return 1;
+    if (attr->bottom > 223)
+        attr->bottom = 223;
+    if (attr->top < attr->gy)
+        attr->top = attr->gy;
+
+    /* Validate width is positive */
+    attr->w = SignExtend(busReadBuffer(world + 14, VB_U16),
+        attr->bgm == 2 ? 10 : 13) + 1;
+    if (attr->w < 1)
+        return 1;
+
+    /* Parse attributes */
+    attr->bg   = (uint8_t *) BG_TEMPLATES[bits >> 8 & 15];
+    attr->gx   = SignExtend(busReadBuffer(world + 2, VB_U16), 10);
+    attr->gp   = SignExtend(busReadBuffer(world + 4, VB_U16), 10);
+    attr->over = (bits & 0x0080) == 0 ? NULL :
+        &sim->vip.ram[0x00020000 | busReadBuffer(world + 10, VB_U16) << 1];
+    attr->scx  = bits >> 10 & 3;
+    attr->scy  = bits >>  8 & 3;
+    attr->bgw  = (1 << attr->scx) - 1;
+    attr->bgh  = (1 << attr->scy) - 1;
+    z = attr->scx + attr->scy;
+    attr->base = bits & 15 & ~((1 << (z < 3 ? z : 3)) - 1);
+    if (attr->bgm != 2) {
+        attr->mx = SignExtend(busReadBuffer(world +  8, VB_U16), 13);
+        attr->mp = SignExtend(busReadBuffer(world + 10, VB_U16), 15);
+        attr->my = SignExtend(busReadBuffer(world + 12, VB_U16), 13);
+    }
+    if (attr->bgm != 0) {
+        attr->params =
+            0x20000 +
+            (attr->top - attr->gy) * (attr->bgm == 1 ? 4 : 16) +
+            ((uint32_t) busReadBuffer(world + 18, VB_U16) << 1)
+        ;
+    }
+
+    return 0;
+}
+
 /* Draw an object group into shadow memory */
 static void vipDrawObjects(VB *sim, int group) {
     uint8_t *dest;       /* Pointer to object position in shadow memory */
@@ -687,124 +800,56 @@ static void vipDrawObjects(VB *sim, int group) {
 }
 
 /* Draw a background world into shadow memory */
-static void vipDrawWorld(VB *sim, uint8_t *world, uint16_t attr) {
-    uint8_t *bg;      /* Background arrangement */
+static void vipDrawWorld(VB *sim, uint8_t *world, uint16_t bits) {
     uint16_t   bgAttr;  /* BG map cell attributes */
-    int32_t  bgh;     /* Height of background in BG maps, minus 1 */
-    int32_t  bgw;     /* Width of background in BG maps, minus 1 */
-    int32_t  bottom;  /* Window bottom edge position */
-    int32_t  bp;      /* Eye BG map source parallax */
-    int32_t  bx;      /* BG horizontal map source position */
-    int32_t  by;      /* BG vertical map source position */
+    int32_t    bx;      /* BG source X */
+    int32_t    by;      /* BG source Y */
     uint8_t   *cell;    /* Pointer to BG map cell in host memory */
     uint8_t   *chr;     /* Pointer to character data in host memory */
-    int32_t  cx;      /* BG cell/character horizontal pixel source position */
-    int32_t  cy;      /* BG cell/character vertical pixel source position */
+    int32_t    cx;      /* BG cell/character source X */
+    int32_t    cy;      /* BG cell/character source Y */
     uint8_t   *dest;    /* Pointer to output in shadow memory */
-    int32_t  left;    /* Window left edge position */
+    EyeAttribs ettr;    /* Eye attributes */
     uint32_t   param;   /* Current line parameter address */
     int8_t     pixel;   /* Character pixel value */
-    int32_t  right;   /* Window right edge position */
-    int32_t  top;     /* Window top edge position */
-    int32_t  wx;      /* Eye horizontal position */
     int32_t    i, x, y; /* Iterators */
 
     /* World attributes */
-    int32_t  base;       /* BG map base index */
-    int      bgm;        /* BG mode */
+    WorldAttribs wttr;  /* Common attributes */
     int32_t      dx;    /* Affine per-pixel X delta */
     int32_t      dy;    /* Affine per-pixel Y delta */
-    int16_t  gp;         /* Window stereo parallax */
-    int16_t  gx;         /* Window base horizontal position */
-    int16_t  gy;         /* Window vertical position */
-    int16_t  h;          /* Window height */
+    int32_t      mp;    /* BG source parallax */
+    int32_t      mx;    /* BG source X */
+    int32_t      my;    /* BG source Y */
     int16_t      hofst; /* H-bias shift */
-    int32_t  mp;         /* BG map source stereo parallax */
-    int32_t  mx = 0;     /* BG map horizontal source */
-    int32_t  my = 0;     /* BG map vertical source */
-    int32_t  scx;        /* Background width shift amount */
-    int32_t  scy;        /* Background height shift amount */
-    uint8_t *over;       /* Pointer to overplane "cell" in host memory */
-    uint32_t params = 0; /* Base address of line parameters */
-    int16_t  w;          /* Window width */
 
-    /* Validate the world isn't below the frame */
-    gy = busReadBuffer(world + 6, VB_S16);
-    if (gy > 223)
-        return;
-
-    /* Validate the world isn't above the frame, and height is positive */
-    bgm = attr >> 12 & 3;
-    y   = bgm == 2 ? 0 : 8;
-    h   = busReadBuffer(world + 16, VB_S16) + 1;
-    if (h < y)
-        h = y;
-    if (h == 0)
-        return;
-    bottom = gy + h - 1;
-    top    = (int32_t) sim->vip.xp.sbcount << 3;
-    if (bottom < top)
-        return;
-    if (bottom > 223)
-        bottom = 223;
-    if (top < gy)
-        top = gy;
-
-    /* Validate width is positive */
-    w = SignExtend(busReadBuffer(world + 14, VB_U16), bgm == 2 ? 10 : 13) + 1;
-    if (w < 1)
-        return;
+    /* Working variables */
+    ettr.bp = wttr.mp = wttr.mx = wttr.my = wttr.params = 0;
 
     /* Parse attributes */
-    bg   = (uint8_t *) BG_TEMPLATES[attr >> 8 & 15];
-    gx   = SignExtend(busReadBuffer(world + 2, VB_U16), 10);
-    gp   = SignExtend(busReadBuffer(world + 4, VB_U16), 10);
-    over = (attr & 0x0080) ? world + 20 : NULL;
-    scx  = attr >> 10 & 3;
-    scy  = attr >>  8 & 3;
-    bgw  = (1 << scx) - 1;
-    bgh  = (1 << scy) - 1;
-    base = attr & 15 & ~((1 << (scx + scy < 3 ? scx + scy : 3)) - 1);
-    if (bgm != 2) {
-        mx = SignExtend(busReadBuffer(world +  8, VB_U16), 13);
-        mp = SignExtend(busReadBuffer(world + 10, VB_U16), 15);
-        my = SignExtend(busReadBuffer(world + 12, VB_U16), 13);
-    }
-    if (bgm != 0) {
-        params = 0x20000 + (top - gy) * (bgm == 1 ? 4 : 16) +
-            ((uint32_t) busReadBuffer(world + 18, VB_U16) << 1);
-    }
-    else hofst = 0;
+    if (vipParseWorld(sim, world, bits, &wttr))
+        return; /* Window not in frame */
 
     /* Draw the world */
     for (i = 0; i < 2; i++) {
 
-        /* Validate world is enabled */
-        if ((attr & (int32_t) 0x8000 >> i) == 0) /* LON, RON */
+        /* World is not visible */
+        if ((bits & (int32_t) 0x8000 >> i) == 0) /* LON, RON */
             continue;
 
-        /* Validate the world isn't right of frame */
-        wx = gx - (i == 0 ? gp : -gp);
-        if (wx > 383)
-            return;
-        left = wx < 0 ? 0 : wx;
-
-        /* Validate the world isn't left of frame */
-        right = wx + w - 1;
-        if (right < 0)
-            return;
-        if (right > 383)
-            right = 383;
-
-        /* BG source parallax */
-        if (bgm != 2)
-            bp = i == 0 ? -mp : mp;
+        /* Process attributes */
+        if (vipParseEye(&wttr, &ettr, i))
+            continue;
 
         /* Draw all rows */
-        for (y = top, param = params; y <= bottom; y++) {
+        for (y = wttr.top, param = wttr.params; y <= wttr.bottom; y++) {
 
             /* Parse line parameters */
-            switch (bgm) {
+            hofst = 0;
+            mp    = wttr.mp;
+            mx    = wttr.mx;
+            my    = wttr.my;
+            switch (wttr.bgm) {
                 case 1: /* H-bias */
                     hofst  = SignExtend(vipParam(param | i << 1), 13);
                     param += 4;
@@ -813,22 +858,22 @@ static void vipDrawWorld(VB *sim, uint8_t *world, uint16_t attr) {
                     dx =  (int32_t) (int16_t) vipParam(param|6) << 7;
                     dy =  (int32_t) (int16_t) vipParam(param|8) << 7;
                     mp =  (int32_t) (int16_t) vipParam(param|2);
-                    mp = left - wx - ((mp < 0) ^ i ? mp : 0);
+                    mp = ettr.left - ettr.wx - ((mp < 0) ^ i ? mp : 0);
                     mx = ((int32_t) (int16_t) vipParam(param  ) << 13) + dx*mp;
                     my = ((int32_t) (int16_t) vipParam(param|4) << 13) + dy*mp;
                     param += 16;
             }
 
             /* Select output in shadow memory */
-            dest = &sim->vip.shadow[i][left * 224 + y];
+            dest = &sim->vip.shadow[i][ettr.left * 224 + y];
 
             /* Draw all columns */
-            for (x = left; x <= right; x++, dest += 224) {
+            for (x = ettr.left; x <= ettr.right; x++, dest += 224) {
 
                 /* Locate the pixel in the background */
-                if (bgm != 2) { /* Normal, H-bias */
-                    cx  = x - wx + mx + bp + hofst;
-                    cy  = y - gy + my;
+                if (wttr.bgm != 2) { /* Normal, H-bias */
+                    cx  = x - ettr.wx + mx + ettr.bp + hofst;
+                    cy  = y - wttr.gy + my;
                 } else { /* Affine */
                     cx  = (int16_t) (mx >> 16);
                     cy  = (int16_t) (my >> 16);
@@ -842,22 +887,23 @@ static void vipDrawWorld(VB *sim, uint8_t *world, uint16_t attr) {
                 cell = NULL;
 
                 /* BG map is out of bounds */
-                if (bx < 0 || bx > bgw || by < 0 || by > bgh) {
-                    if (over == NULL) {
-                        bx &= bgw;
-                        by &= bgh;
-                    }
-                    else {
-                        cell = over;
-                        continue; /* TODO: Research overplane */
-                    }
+                if (
+                    bx < 0 || bx > wttr.bgw ||
+                    by < 0 || by > wttr.bgh
+                ) {
+                    if (wttr.over == NULL) {
+                        bx &= wttr.bgw;
+                        by &= wttr.bgh;
+                    } else cell = wttr.over;
                 }
 
                 /* Locate the cell in the BG map */
                 if (cell == NULL) {
                     cell = &sim->vip.ram[
-                        0x20000                           |
-                        (base + bg[by << scx | bx]) << 13 |
+                        0x20000 | ((
+                            wttr.base +
+                            wttr.bg[by << wttr.scx | bx]
+                        ) << 13) |
                         (cy << 4 & 0x1F80) |
                         (cx >> 2 & 0x007E)
                     ];

core/vsu.c

@@ -368,8 +368,21 @@ static void vsuEmulate(VB *sim, uint32_t clocks) {
                 sim->vsu.out.samples != NULL &&
                 sim->vsu.out.offset >> 1 < sim->vsu.out.capacity
             ) {
-                sim->vsu.out.samples[sim->vsu.out.offset++] =
-                    (int16_t) (o0 * 32767.0f + (o0 < 0.0f ? -0.5f : +0.5f));
+
+                /* Processing by data type*/
+                switch (sim->vsu.out.type) {
+                    case VB_S16:
+                        ((int16_t *) sim->vsu.out.samples)
+                        [sim->vsu.out.offset++] = (int16_t)
+                        (o0 * 32767.0f + (o0 < 0.0f ? -0.5f : +0.5f));
+                        break;
+                    case VB_F32:
+                        ((float *) sim->vsu.out.samples)
+                        [sim->vsu.out.offset++] = o0;
+                        break;
+                }
+
+                /* Invoke the samples callback */
                 if (
                     e == 1 &&
                     sim->vsu.out.offset >> 1 == sim->vsu.out.capacity

makefile

@@ -10,6 +10,7 @@ help:
 	@echo "Available make targets:"
 	@echo "  clean   Remove output files"
 	@echo "  core    Check the C core source for compiler warnings"
+	@echo "  util    Check the C utility source for compiler warnings"
 	@echo "  wasm    Build the WebAssembly module"
 	@echo
 
@@ -29,7 +30,7 @@ core:
         -D VB_DIRECT_EXCEPTION=textException -D VB_DIRECT_EXECUTE=textExecute \
         -D VB_DIRECT_FETCH=testFetch -D VB_DIRECT_FRAME=testFrame \
         -D VB_DIRECT_WRITE=testWrite -D VB_DIRECT_SAMPLES=testSamples \
-        -D VB_DIRECT_READ=testRead
+        -D VB_DIRECT_READ=testRead -D VB_DIRECT_LINK=testLink
 #	Clang generic
 	@emcc core/vb.c -I core -c -o /dev/null -O3 \
         -Werror -std=c90 -Wall -Wextra -Wpedantic -fno-strict-aliasing
@@ -40,14 +41,32 @@ core:
         -D VB_DIRECT_EXCEPTION=textException -D VB_DIRECT_EXECUTE=textExecute \
         -D VB_DIRECT_FETCH=testFetch -D VB_DIRECT_FRAME=testFrame \
         -D VB_DIRECT_WRITE=testWrite -D VB_DIRECT_SAMPLES=testSamples \
-        -D VB_DIRECT_READ=testRead
+        -D VB_DIRECT_READ=testRead -D VB_DIRECT_LINK=testLink
+
+.PHONY: util
+util:
+#	GCC generic
+	@gcc util/vbu.c -I core -I util -c -o /dev/null -O3 \
+        -Werror -std=c90 -Wall -Wextra -Wpedantic -fno-strict-aliasing
+#	GCC compilation control
+	@gcc util/vbu.c -I core -I util -c -o /dev/null -O3 \
+        -Werror -std=c90 -Wall -Wextra -Wpedantic -fno-strict-aliasing \
+        -D VB_SIGNED_PROPAGATE -D VBU_REALLOC=testRealloc
+#	Clang generic
+	@emcc util/vbu.c -I core -I util -c -o /dev/null -O3 \
+        -Werror -std=c90 -Wall -Wextra -Wpedantic -fno-strict-aliasing
+#	Clang compilation control
+	@emcc util/vbu.c -I core -I util -c -o /dev/null -O3 \
+        -Werror -std=c90 -Wall -Wextra -Wpedantic -fno-strict-aliasing \
+        -D VB_SIGNED_PROPAGATE -D VBU_REALLOC=testRealloc
 
 .PHONY: wasm
 wasm:
-	@emcc -o web/core.wasm web/wasm.c core/vb.c -I core \
+	@emcc -o web/core.wasm web/wasm.c core/vb.c util/vbu.c -I core -I util \
         -D VB_LITTLE_ENDIAN -D VB_SIGNED_PROPAGATE \
-        -D "VBAPI=__attribute__((used))" \
-        --no-entry -O2 -flto -s WASM=1 -s WARN_ON_UNDEFINED_SYMBOLS=0 \
+        -D "VBAPI=__attribute__((used))" -D "VBUAPI=__attribute__((used))" \
+        -D VB_DIRECT_FRAME=wasmOnFrame \
+        --no-entry -O2 -flto -s WASM=1 \
         -s EXPORTED_RUNTIME_METHODS=[] -s ALLOW_MEMORY_GROWTH \
         -s MAXIMUM_MEMORY=4GB -fno-strict-aliasing
 	@rm -f web/*.wasm.tmp*

util/disassembler.c

@@ -0,0 +1,694 @@
+/* This file is included into vb.c and cannot be compiled on its own. */
+#ifdef VBUAPI
+
+
+
+/********************************* Constants *********************************/
+
+/* Operand types */
+#define DASM_BCOND   0
+#define DASM_DISP9   1
+#define DASM_DISP26  2
+#define DASM_IMM5S   3
+#define DASM_IMM5U   4
+#define DASM_IMM16S  5
+#define DASM_IMM16U  6
+#define DASM_JMP     7
+#define DASM_MEMORY  8
+#define DASM_REG1    9
+#define DASM_REG2   10
+#define DASM_SETF   11
+#define DASM_SYSTEM 12
+
+
+
+/******************************** Lookup Data ********************************/
+
+/* Instruction descriptor */
+typedef struct {
+    char    mnemonic[8];    /* Mnemonic, uppercase */
+    uint8_t operandsLength; /* Number of operands */
+    uint8_t operands[3];    /* Operand types */
+} OpDef;
+
+/* Instruction descriptors */
+static const OpDef OPDEFS[] = {
+    { "MOV"  , 2, { DASM_REG1, DASM_REG2 } },   /* 000000 */
+    { "ADD"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "SUB"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "CMP"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "SHL"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "SHR"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "JMP"  , 1, { DASM_JMP } },
+    { "SAR"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "MUL"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "DIV"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "MULU" , 2, { DASM_REG1, DASM_REG2 } },
+    { "DIVU" , 2, { DASM_REG1, DASM_REG2 } },
+    { "OR"   , 2, { DASM_REG1, DASM_REG2 } },
+    { "AND"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "XOR"  , 2, { DASM_REG1, DASM_REG2 } },
+    { "NOT"  , 1, { DASM_REG1 } },
+
+    { "MOV"  , 2, { DASM_IMM5S, DASM_REG2 } },  /* 010000 */
+    { "ADD"  , 2, { DASM_IMM5S, DASM_REG2 } },
+    { ""     , 0, { 0 } }, /* SETF */
+    { "CMP"  , 2, { DASM_IMM5S, DASM_REG2 } },
+    { "SHL"  , 2, { DASM_IMM5U, DASM_REG2 } },
+    { "SHR"  , 2, { DASM_IMM5U, DASM_REG2 } },
+    { "CLI"  , 0, { 0 } },
+    { "SAR"  , 2, { DASM_IMM5U, DASM_REG2 } },
+    { "TRAP" , 1, { DASM_IMM5U } },
+    { "RETI" , 0, { 0 } },
+    { "HALT" , 0, { 0 } },
+    { "---"  , 0, { 0 } },
+    { "LDSR" , 2, { DASM_REG2, DASM_SYSTEM } },
+    { "STSR" , 2, { DASM_SYSTEM, DASM_REG2 } },
+    { "SEI"  , 0, { 0 } },
+    { ""     , 0, { 0 } }, /* Bit string */
+
+    { ""     , 0, { 0 } }, /* BCOND */          /* 100000 */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { ""     , 0, { 0 } }, /* BCOND */
+    { "MOVEA", 3, { DASM_IMM16U, DASM_REG1, DASM_REG2 } },
+    { "ADDI" , 3, { DASM_IMM16S, DASM_REG1, DASM_REG2 } },
+    { "JR"   , 1, { DASM_DISP26 } },
+    { "JAL"  , 1, { DASM_DISP26 } },
+    { "ORI"  , 3, { DASM_IMM16U, DASM_REG1, DASM_REG2 } },
+    { "ANDI" , 3, { DASM_IMM16U, DASM_REG1, DASM_REG2 } },
+    { "XORI" , 3, { DASM_IMM16U, DASM_REG1, DASM_REG2 } },
+    { "MOVHI", 3, { DASM_IMM16U, DASM_REG1, DASM_REG2 } },
+
+    { "LD.B" , 2, { DASM_MEMORY, DASM_REG2 } }, /* 110000 */
+    { "LD.H" , 2, { DASM_MEMORY, DASM_REG2 } },
+    { "---"  , 0, { 0 } },
+    { "LD.W" , 2, { DASM_MEMORY, DASM_REG2 } },
+    { "ST.B" , 2, { DASM_REG2, DASM_MEMORY } },
+    { "ST.H" , 2, { DASM_REG2, DASM_MEMORY } },
+    { "---"  , 0, { 0 } },
+    { "ST.W" , 2, { DASM_REG2, DASM_MEMORY } },
+    { "IN.B" , 2, { DASM_MEMORY, DASM_REG2 } },
+    { "IN.H" , 2, { DASM_MEMORY, DASM_REG2 } },
+    { "CAXI" , 0, { DASM_MEMORY, DASM_REG2 } },
+    { "IN.W" , 2, { DASM_MEMORY, DASM_REG2 } },
+    { "OUT.B", 2, { DASM_REG2, DASM_MEMORY } },
+    { "OUT.H", 2, { DASM_REG2, DASM_MEMORY } },
+    { ""     , 0, { 0 } }, /* Floating-point/Nintendo */
+    { "OUT.W", 2, { DASM_REG2, DASM_MEMORY } }
+};
+
+/* Bit string instruction descriptors */
+static const OpDef OPDEFS_BITSTRING[] = {
+    { "SCH0BSU", 0, { 0 } }, /* 00000 */
+    { "SCH0BSD", 0, { 0 } },
+    { "SCH1BSU", 0, { 0 } },
+    { "SCH1BSD", 0, { 0 } },
+    { "---"    , 0, { 0 } },
+    { "---"    , 0, { 0 } },
+    { "---"    , 0, { 0 } },
+    { "---"    , 0, { 0 } },
+    { "ORBSU"  , 0, { 0 } },
+    { "ANDBSU" , 0, { 0 } },
+    { "XORBSU" , 0, { 0 } },
+    { "MOVBSU" , 0, { 0 } },
+    { "ORNBSU" , 0, { 0 } },
+    { "ANDNBSU", 0, { 0 } },
+    { "XORNBSU", 0, { 0 } },
+    { "NOTBSU" , 0, { 0 } }
+    /* +16 invalid opcodes */
+};
+
+/* Floating-point/Nintendo instruction descriptors */
+static const OpDef OPDEFS_FLOATENDO[] = {
+    { "CMPF.S" , 2, { DASM_REG1, DASM_REG2 } },
+    { "---"    , 0, { 0 } },
+    { "CVT.WS" , 2, { DASM_REG1, DASM_REG2 } },
+    { "CVT.SW" , 2, { DASM_REG1, DASM_REG2 } },
+    { "ADDF.S" , 2, { DASM_REG1, DASM_REG2 } },
+    { "SUBF.S" , 2, { DASM_REG1, DASM_REG2 } },
+    { "MULF.S" , 2, { DASM_REG1, DASM_REG2 } },
+    { "DIVF.S" , 2, { DASM_REG1, DASM_REG2 } },
+    { "XB"     , 1, { DASM_REG2 } },
+    { "XH"     , 1, { DASM_REG2 } },
+    { "REV"    , 2, { DASM_REG1, DASM_REG2 } },
+    { "TRNC.SW", 2, { DASM_REG1, DASM_REG2 } },
+    { "MPYHW"  , 2, { DASM_REG1, DASM_REG2 } },
+    /* +51 invalid opcodes */
+};
+
+/* Invalid instruction descriptors */
+static const OpDef OPDEF_ILLEGAL = { "---", 0, { 0 } };
+
+
+
+/***************************** Module Functions ******************************/
+
+/* Select the display text for a condition */
+static char* dasmCondition(VBU_DasmConfig *config, int cond) {
+    switch (cond) {
+        case  0: return "V" ;
+        case  1: return config->conditionCL == VBU_C ? "C" : "L";
+        case  2: return config->conditionEZ == VBU_E ? "E" : "Z";
+        case  3: return "NH";
+        case  4: return "N" ;
+        case  5: return "T" ;
+        case  6: return "LT";
+        case  7: return "LE";
+        case  8: return "NV";
+        case  9: return config->conditionCL == VBU_C ? "NC" : "NL";
+        case 10: return config->conditionEZ == VBU_E ? "NE" : "NZ";
+        case 11: return "H" ;
+        case 12: return "P" ;
+        case 13: return "F" ;
+        case 14: return "GE";
+    }
+    return "GT";
+}
+
+/* Format a number as hexadecimal */
+static void dasmToHex(char *dest, VBU_DasmConfig *config,
+    int minDigits, int32_t value) {
+    char  format[9];
+    char *prefix = "";
+    char *suffix = "";
+    switch (config->hexNotation) {
+        case VBU_0X    : prefix = "0x"; break;
+        case VBU_DOLLAR: prefix = "$" ; break;
+        case VBU_H     : suffix = "h" ; break;
+    }
+    sprintf(format, "%%s%%0%d%s%%s", minDigits,
+        config->hexCase == VBU_LOWER ? "x" : "X");
+    sprintf(dest, format, prefix, value, suffix);
+    if (config->hexNotation != VBU_H || *dest <= '9')
+        return;
+    *dest++ = '0';
+    sprintf(dest, format, prefix, value, suffix);
+}
+
+/* Convert a string to lowercase */
+static void dasmToLower(char *str) {
+    for (; *str; str++) {
+        if (*str >= 'A' && *str <= 'Z')
+            *str += 'a' - 'A';
+    }
+}
+
+/* Format a program register */
+static void dasmProgram(char *dest, VBU_DasmConfig *config, int id) {
+    char *text = NULL;
+    if (config->programNotation != VBU_NUMBERS) {
+        switch (id) {
+            case  2: text = "HP"; break;
+            case  3: text = "SP"; break;
+            case  4: text = "GP"; break;
+            case  5: text = "TP"; break;
+            case 31: text = "LP"; break;
+        }
+    }
+    if (text == NULL)
+        sprintf(dest, "R%d", id);
+    else strcpy(dest, text);
+    if (config->programCase == VBU_LOWER)
+        dasmToLower(dest);
+}
+
+
+
+/**************************** Operand Formatters *****************************/
+
+/* Format the condition operand of a split BCOND instruction */
+static void dasmOpBCOND(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int cond = line->code[1] >> 2 & 15;
+    if (config->conditionNotation == VBU_NUMBERS)
+        sprintf(dest, "%d", cond);
+    else {
+        strcpy(dest, dasmCondition(config, cond));
+        if (config->conditionCase == VBU_LOWER)
+            dasmToLower(dest);
+    }
+}
+
+/* Format a 9-bit displacement operand */
+static void dasmOpDisp9(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int32_t disp = SignExtend((int32_t) line->code[1] << 8 | line->code[0], 9);
+    sprintf(dest, config->hexCase == VBU_LOWER ?
+        "%08x" : "%08X", line->address + disp);
+}
+
+/* Format a 26-bit displacement operand */
+static void dasmOpDisp26(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int32_t disp = SignExtend(
+        (int32_t) line->code[1] << 24 |
+        (int32_t) line->code[0] << 16 |
+        (int32_t) line->code[3] <<  8 |
+                  line->code[2]
+    , 26);
+    sprintf(dest, config->hexCase == VBU_LOWER ?
+        "%08x" : "%08X", line->address + disp);
+}
+
+/* Format a 5-bit sign-extended immediate operand */
+static void dasmOpImm5S(char *dest, VBU_DasmLine *line) {
+    sprintf(dest, "%d", SignExtend(line->code[0], 5));
+}
+
+/* Format a 5-bit zero-filled immediate operand */
+static void dasmOpImm5U(char *dest, VBU_DasmLine *line) {
+    sprintf(dest, "%d", line->code[0] & 31);
+}
+
+/* Format a 16-bit sign-extended immediate operand */
+static void dasmOpImm16S(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int32_t imm = (int16_t) ((int16_t) line->code[3] << 8 | line->code[2]);
+    if (imm >= -256 && imm <= 256) {
+        sprintf(dest, "%d", imm);
+        return;
+    }
+    if (imm < 0) {
+        *dest++ = '-';
+        imm     = -imm;
+    }
+    dasmToHex(dest, config, 0, imm);
+}
+
+/* Format a 16-bit zero-filled immediate operand */
+static void dasmOpImm16U(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    uint16_t imm = (uint16_t) line->code[3] << 8 | line->code[2];
+    dasmToHex(dest, config, 4, imm);
+}
+
+/* Format the operand of a JMP instruction */
+static void dasmOpJMP(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    *dest++ = '[';
+    dasmProgram(dest, config, line->code[0] & 31);
+    strcat(dest, "]");
+}
+
+/* Format a memory operand */
+static void dasmOpMemory(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int     reg1 = line->code[0] & 31;
+    int32_t disp = (int16_t) ((int16_t) line->code[3] << 8 | line->code[2]);
+
+    /* Displacement of zero */
+    if (disp == 0) {
+        *dest++ = '[';
+        dasmProgram(dest, config, reg1);
+        strcat(dest, "]");
+        return;
+    }
+
+    /* Inside */
+    if (config->memoryNotation == VBU_INSIDE) {
+        *dest++ = '[';
+        dasmProgram(dest, config, reg1);
+        dest += strlen(dest);
+        if (disp < 0) {
+            strcpy(dest, " - ");
+            disp = -disp;
+        } else strcpy(dest, " + ");
+        dest += 3;
+        if (disp <= 256)
+            sprintf(dest, "%d", disp);
+        else dasmToHex(dest, config, 0, disp);
+        strcat(dest, "]");
+    }
+
+    /* Outside */
+    else {
+        if (disp < 0) {
+            *dest++ = '-';
+            disp = -disp;
+        }
+        if (disp <= 256)
+            sprintf(dest, "%d", disp);
+        else dasmToHex(dest, config, 0, disp);
+        dest += strlen(dest);
+        *dest++ = '[';
+        dasmProgram(dest, config, reg1);
+        strcat(dest, "]");
+    }
+
+}
+
+/* Format a source register operand */
+static void dasmOpReg1(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    dasmProgram(dest, config, line->code[0] & 31);
+}
+
+/* Format a destination register operand */
+static void dasmOpReg2(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    dasmProgram(dest, config,
+        ((uint16_t) line->code[1] << 8 | line->code[0]) >> 5 & 31);
+}
+
+/* Format the condition operand of a split SETF instruction */
+static void dasmOpSETF(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int cond = line->code[0] & 15;
+    if (config->conditionNotation == VBU_NUMBERS)
+        sprintf(dest, "%d", cond);
+    else {
+        strcpy(dest, dasmCondition(config, cond));
+        if (config->conditionCase == VBU_LOWER)
+            dasmToLower(dest);
+    }
+}
+
+/* Format a system register operand */
+static void dasmOpSystem(char*dest, VBU_DasmConfig*config, VBU_DasmLine*line) {
+    int   id   = line->code[0] & 31;
+    char *text = NULL;
+    if (config->systemNotation != VBU_NUMBERS) {
+        switch (id) {
+            case  0: text = "EIPC" ; break;
+            case  1: text = "EIPSW"; break;
+            case  2: text = "FEPC" ; break;
+            case  3: text = "FEPSW"; break;
+            case  4: text = "ECR"  ; break;
+            case  5: text = "PSW"  ; break;
+            case  6: text = "PIR"  ; break;
+            case  7: text = "TKCW" ; break;
+            case 24: text = "CHCW" ; break;
+            case 25: text = "ADTRE"; break;
+        }
+    }
+    if (text == NULL) {
+        sprintf(dest, "%d", id);
+        return;
+    }
+    strcpy(dest, text);
+    if (config->systemCase == VBU_LOWER)
+        dasmToLower(dest);
+}
+
+
+
+/***************************** Module Functions ******************************/
+
+/* Prepare an OpDef for a BCOND instruction */
+static OpDef* dasmBCOND(VBU_DasmConfig *config,
+    VBU_DasmLine *line, OpDef *opdef) {
+    int   cond; /* Condition code */
+    char *text; /* Mnemonic text */
+
+    /* Split notation */
+    if (config->bcondNotation == VBU_SPLIT) {
+        strcpy(opdef->mnemonic, "BCOND");
+        opdef->operandsLength = 2;
+        opdef->operands[0] = DASM_BCOND;
+        opdef->operands[1] = DASM_DISP9;
+        return opdef;
+    }
+
+    /* Joined notation */
+    cond = line->code[1] >> 1 & 15;
+    switch (cond) {
+        case  0: text = "BV" ; break;
+        case  1: text = config->conditionCL == VBU_C ? "BC" : "BL"; break;
+        case  2: text = config->conditionEZ == VBU_E ? "BE" : "BZ"; break;
+        case  3: text = "BNH"; break;
+        case  4: text = "BN" ; break;
+        case  5: text = "BR" ; break;
+        case  6: text = "BLT"; break;
+        case  7: text = "BLE"; break;
+        case  8: text = "BNV"; break;
+        case  9: text = config->conditionCL == VBU_C ? "BNC" : "BNL"; break;
+        case 10: text = config->conditionEZ == VBU_E ? "BNE" : "BNZ"; break;
+        case 11: text = "BH" ; break;
+        case 12: text = "BP" ; break;
+        case 13: text = "NOP"; break;
+        case 14: text = "BGE"; break;
+        default: text = "BGT";
+    }
+    strcpy(opdef->mnemonic, text);
+    opdef->operandsLength = cond != 13;
+    opdef->operands[0]   = DASM_DISP9;
+    return opdef;
+}
+
+/* Ensure an output buffer matches the required size */
+static VBU_DasmLine* dasmGrow(
+    VBU_DasmLine **lines, size_t *size, size_t target, unsigned index) {
+    if (*size < target) {
+        while (*size < target)
+            *size *= 2;
+        *lines = VBU_REALLOC(*lines, *size);
+    }
+    return *lines == NULL ? NULL : &(*lines)[index];
+}
+
+/* Determine the size of an instruction */
+static uint32_t dasmInstSize(VB *sim, uint32_t address) {
+    unsigned opcode = vbRead(sim, address, VB_U16) >> 10 & 63;
+    return opcode < 0x20 || opcode == 0x32 || opcode == 0x36 ? 2 : 4;
+}
+
+/* Format an operand */
+static void dasmOperand(char *dest, VBU_DasmConfig *config,
+    VBU_DasmLine *line, uint8_t type) {
+    switch (type) {
+        case DASM_BCOND : dasmOpBCOND (dest, config, line); break;
+        case DASM_DISP9 : dasmOpDisp9 (dest, config, line); break;
+        case DASM_DISP26: dasmOpDisp26(dest, config, line); break;
+        case DASM_IMM5S : dasmOpImm5S (dest,         line); break;
+        case DASM_IMM5U : dasmOpImm5U (dest,         line); break;
+        case DASM_IMM16S: dasmOpImm16S(dest, config, line); break;
+        case DASM_IMM16U: dasmOpImm16U(dest, config, line); break;
+        case DASM_JMP   : dasmOpJMP   (dest, config, line); break;
+        case DASM_MEMORY: dasmOpMemory(dest, config, line); break;
+        case DASM_REG1  : dasmOpReg1  (dest, config, line); break;
+        case DASM_REG2  : dasmOpReg2  (dest, config, line); break;
+        case DASM_SETF  : dasmOpSETF  (dest, config, line); break;
+        case DASM_SYSTEM: dasmOpSystem(dest, config, line); break;
+    }
+}
+
+/* Prepare an OpDef for a SETF instruction */
+static OpDef* dasmSETF(VBU_DasmConfig *config,
+    VBU_DasmLine *line, OpDef *opdef) {
+
+    /* Split notation */
+    if (config->bcondNotation == VBU_SPLIT) {
+        strcpy(opdef->mnemonic, "SETF");
+        opdef->operandsLength = 2;
+        opdef->operands[0] = DASM_SETF;
+        opdef->operands[1] = DASM_REG2;
+        return opdef;
+    }
+
+    /* Joined notation */
+    sprintf(opdef->mnemonic, "SETF%s",
+        dasmCondition(config, line->code[1] >> 1 & 15));
+    opdef->operandsLength = 1;
+    opdef->operands[0]   = DASM_REG2;
+    return opdef;
+}
+
+/* Disassemble one instruction */
+static int dasmLine(VB *sim, uint32_t *address, uint32_t pc,
+    VBU_DasmConfig *config, VBU_DasmLine **lines, size_t *size, size_t *offset,
+    unsigned index) {
+    char         *dest;             /* Text output pointer */
+    char         *format;           /* Hexadecimal format string */
+    VBU_DasmLine *line;             /* Output line */
+    size_t        more;             /* Number of bytes to output */
+    OpDef        *opdef;            /* Instruction descriptor */
+    OpDef         special;          /* Special-case descriptor */
+    char          tAddress[9];      /* Address display text */
+    char          tCode[4][3];      /* Code display text */
+    char          tMnemonic[8];     /* Mnemonic display text */
+    char          tOperands[3][15]; /* Operands display text */
+    uint32_t      x;                /* Scratch and iterator */
+
+    /* Process non-text members */
+    line = &(*lines)[index];
+    line->address    = *address;
+    line->codeLength = dasmInstSize(sim, *address);
+    line->isPC       = *address == pc;
+    for (x = 0; x < line->codeLength; x++)
+        line->code[x] = vbRead(sim, *address + x, VB_U8);
+    *address += pc - *address < line->codeLength ?
+        pc - *address : line->codeLength;
+
+    /* Do not process text members */
+    if (config == NULL) {
+        line->text.address        = NULL;
+        line->text.mnemonic       = NULL;
+        line->text.operandsLength = 0;
+        for (x = 0; x < line->codeLength; x++)
+            line->text.code[x] = NULL;
+        return 0;
+    }
+
+    /* Select instruction descriptor */
+    x = line->code[1] >> 2 & 63;
+    switch (x) {
+        case 0x12: /* SETF */
+            opdef = dasmSETF(config, line, &special);
+            break;
+        case 0x1F: /* Bit string */
+            x     = line->code[0] & 31;
+            opdef = (OpDef *) (x < 16 ? &OPDEFS_BITSTRING[x] : &OPDEF_ILLEGAL);
+            break;
+        case 0x20: case 0x21: case 0x22: case 0x23: /* BCOND */
+        case 0x24: case 0x25: case 0x26: case 0x27:
+            opdef = dasmBCOND(config, line, &special);
+            break;
+        case 0x3E: /* Floating-point/Nintendo */
+            x = line->code[3] >> 2 & 63;
+            opdef = (OpDef *) (x < 13 ? &OPDEFS_FLOATENDO[x] : &OPDEF_ILLEGAL);
+            break;
+        default: opdef = (OpDef *) &OPDEFS[x]; /* Other */
+    }
+
+    /* Address */
+    format = config->hexCase == VBU_LOWER ? "%08x" : "%08X";
+    sprintf(tAddress, format, line->address);
+    more = 9;
+
+    /* Code */
+    format = config->hexCase == VBU_LOWER ? "%02x" : "%02X";
+    for (x = 0; x < line->codeLength; x++) {
+        sprintf(tCode[x], format, (int) line->code[x]);
+        more += 3;
+    }
+
+    /* Mnemonic */
+    strcpy(tMnemonic, opdef->mnemonic);
+    if (config->mnemonicCase == VBU_LOWER)
+        dasmToLower(tMnemonic);
+    more += strlen(tMnemonic) + 1;
+
+    /* Operands */
+    line->text.operandsLength = opdef->operandsLength;
+    for (x = 0; x < opdef->operandsLength; x++) {
+        dasmOperand(tOperands[x], config, line, opdef->operands[x]);
+        more += strlen(tOperands[x]) + 1;
+    }
+
+    /* Grow the text buffer */
+    line = dasmGrow(lines, size, *offset + more, index);
+    if (line == NULL)
+        return 1;
+
+    /* Working variables */
+    dest     = &((char *) *lines)[*offset];
+    *offset += more;
+
+    /* Address */
+    strcpy(dest, tAddress);
+    line->text.address = dest;
+    dest += 9;
+
+    /* Code */
+    for (x = 0; x < line->codeLength; x++) {
+        strcpy(dest, tCode[x]);
+        line->text.code[x] = dest;
+        dest += 3;
+    }
+
+    /* Mnemonic */
+    strcpy(dest, tMnemonic);
+    line->text.mnemonic = dest;
+    dest += strlen(dest) + 1;
+
+    /* Operands */
+    for (x = 0; x < opdef->operandsLength; x++) {
+        strcpy(dest, tOperands[
+            config->operandOrder == VBU_DEST_FIRST ?
+            opdef->operandsLength - 1 - x :
+            x
+        ]);
+        line->text.operands[x] = dest;
+        dest += strlen(dest) + 1;
+    }
+
+    return 0;
+}
+
+
+
+/***************************** Library Functions *****************************/
+
+/* Disassemble from a simulation */
+static VBU_DasmLine* dasmDisassemble(VB *sim, uint32_t address,
+    VBU_DasmConfig *config, unsigned length, int line) {
+    uint32_t      addr;          /* Working address */
+    uint32_t     *circle = NULL; /* Circular address buffer */
+    VBU_DasmLine *lines  = NULL; /* Output line buffer */
+    size_t        offset;        /* Offset into lines buffer */
+    uint32_t      pc;            /* Program counter */
+    size_t        size;          /* Number of bytes in lines */
+    unsigned      x;             /* Iterator */
+
+    /* Nothing to disassemble */
+    if (length == 0)
+        return NULL;
+
+    /* Establish a circular buffer */
+    if (line > 0) {
+        circle = VBU_REALLOC(NULL, (size_t) (line + 1) * sizeof (uint32_t));
+        if (circle == NULL)
+            goto catch;
+    }
+
+    /* Begin decoding from at least 10 lines before first/reference */
+    addr = (address & 0xFFFFFFFE) -
+        (int32_t) (line <= 0 ? 10 : line + 10) * 4;
+
+    /* Locate the address of the line containing the reference address */
+    pc = vbGetProgramCounter(sim);
+    for (x = 0;;) {
+
+        /* Track the address in the circular buffer */
+        if (line > 0) {
+            circle[x] = addr;
+            if (++x > (size_t) line)
+                x = 0;
+        }
+
+        /* Check if the instruction contains the reference address */
+        size = dasmInstSize(sim, addr);
+        if (address - addr < size)
+            break;
+        addr += pc - addr < size ? pc - addr : size;
+    }
+
+    /* Address of first line is in the circular buffer */
+    if (line > 0) {
+        addr   = circle[x];
+        circle = VBU_REALLOC(circle, 0);
+    }
+
+    /* Keep decoding until the first line of output */
+    else for (; line < 0; line++)
+        addr += dasmInstSize(sim, addr);
+
+    /* Working variables */
+    size   = length * sizeof (VBU_DasmLine);
+    lines  = VBU_REALLOC(NULL, size);
+    offset = size;
+    if (lines == NULL)
+        goto catch;
+
+    /* Process output lines */
+    for (x = 0; x < length; x++) {
+        if (dasmLine(sim, &addr, pc, config, &lines, &size, &offset, x))
+            goto catch;
+    }
+    return lines;
+
+    /* Exception handler */
+    catch:
+    circle = VBU_REALLOC(circle, 0);
+    lines  = VBU_REALLOC(lines , 0);
+    return NULL;
+}
+
+
+
+#endif /* VBUAPI */

util/vbu.c

@@ -0,0 +1,65 @@
+#ifndef VBUAPI
+#define VBUAPI
+#endif
+#include <stdio.h>
+#include <string.h>
+#include <vbu.h>
+
+/* Memory management */
+#ifndef VBU_REALLOC
+    #include <stdlib.h>
+    #define VBU_REALLOC realloc
+#else
+    extern void* VBU_REALLOC(void *, size_t);
+#endif
+
+
+
+/***************************** Library Functions *****************************/
+
+/* Sign-extend an integer of variable width */
+static int32_t SignExtend(int32_t value, int32_t bits) {
+    #ifndef VB_SIGNED_PROPAGATE
+        value &= ~((uint32_t) 0xFFFFFFFF << bits);
+        bits   = (int32_t) 1 << (bits - (int32_t) 1);
+        return (value ^ bits) - bits;
+    #else
+        return value << (32 - bits) >> (32 - bits);
+    #endif
+}
+
+
+
+/******************************** Sub-Modules ********************************/
+
+#include "disassembler.c"
+
+
+
+/******************************* API Commands ********************************/
+
+/* Initialize disassembler options with default settings */
+VBUAPI VBU_DasmConfig* vbuDasmInit(VBU_DasmConfig *config) {
+    config->bcondNotation     = VBU_JOINED;
+    config->conditionCase     = VBU_LOWER;
+    config->conditionCL       = VBU_L;
+    config->conditionEZ       = VBU_Z;
+    config->conditionNotation = VBU_NAMES;
+    config->hexCase           = VBU_UPPER;
+    config->hexNotation       = VBU_0X;
+    config->memoryNotation    = VBU_OUTSIDE;
+    config->mnemonicCase      = VBU_UPPER;
+    config->operandOrder      = VBU_DEST_LAST;
+    config->programCase       = VBU_LOWER;
+    config->programNotation   = VBU_NAMES;
+    config->setfNotation      = VBU_SPLIT;
+    config->systemCase        = VBU_LOWER;
+    config->systemNotation    = VBU_NAMES;
+    return config;
+}
+
+/* Disassemble from a simulation */
+VBUAPI VBU_DasmLine* vbuDisassemble(VB *sim, uint32_t address,
+    VBU_DasmConfig *config, unsigned length, int line) {
+    return dasmDisassemble(sim, address, config, length, line);
+}

util/vbu.h

@@ -0,0 +1,94 @@
+#ifndef VBU_H_
+#define VBU_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef VBUAPI
+#define VBUAPI extern
+#endif
+
+/* Header includes */
+#include <vb.h>
+
+
+
+/********************************* Constants *********************************/
+
+/* Disassembler options */
+#define VBU_0X         0
+#define VBU_C          1
+#define VBU_DEST_FIRST 1
+#define VBU_DEST_LAST  0
+#define VBU_DOLLAR     1
+#define VBU_E          0
+#define VBU_H          2
+#define VBU_INSIDE     1
+#define VBU_JOINED     0
+#define VBU_L          0
+#define VBU_LOWER      1
+#define VBU_NAMES      1
+#define VBU_NUMBERS    0
+#define VBU_OUTSIDE    0
+#define VBU_SPLIT      1
+#define VBU_UPPER      0
+#define VBU_Z          1
+
+
+
+/*********************************** Types ***********************************/
+
+/* Disassembler text options */
+typedef struct {               /* Defaults listed first */
+    uint8_t bcondNotation;     /* JOINED, SPLIT */
+    uint8_t conditionCase;     /* LOWER, UPPER */
+    uint8_t conditionCL;       /* L, C */
+    uint8_t conditionEZ;       /* Z, E */
+    uint8_t conditionNotation; /* NAMES, NUMBERS */
+    uint8_t hexCase;           /* UPPER, LOWER */
+    uint8_t hexNotation;       /* 0X, H, DOLLAR */
+    uint8_t memoryNotation;    /* OUTSIDE, INSIDE */
+    uint8_t mnemonicCase;      /* UPPER, LOWER */
+    uint8_t operandOrder;      /* DEST_LAST, DEST_FIRST */
+    uint8_t programCase;       /* LOWER, UPPER */
+    uint8_t programNotation;   /* NAMES, NUMBERS */
+    uint8_t setfNotation;      /* SPLIT, JOINED */
+    uint8_t systemCase;        /* LOWER, UPPER */
+    uint8_t systemNotation;    /* NAMES, NUMBERS */
+} VBU_DasmConfig;
+
+/* Disassembler output line */
+typedef struct {
+
+    /* Parsed */
+    uint32_t address;    /* Memory address */
+    uint16_t code[4];    /* Instruction bytes */
+    uint8_t  codeLength; /* Number of items in code */
+    uint8_t  isPC;       /* Set if PC is on this line */
+
+    /* Display text */
+    struct {
+        char   *address;        /* Memory address */
+        char   *code[4];        /* Instruction bytes */
+        char   *mnemonic;       /* Instruction mnemonic */
+        char   *operands[3];    /* Instruction operands */
+        uint8_t operandsLength; /* Number of items in operands */
+    } text;
+
+} VBU_DasmLine;
+
+
+
+/******************************* API Commands ********************************/
+
+VBUAPI VBU_DasmConfig* vbuDasmInit   (VBU_DasmConfig *config);
+VBUAPI VBU_DasmLine*   vbuDisassemble(VB *sim, uint32_t address, VBU_DasmConfig *config, unsigned length, int line);
+
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* VBU_H_ */