Preliminary CPU implementation

app/_boot.js

@@ -291,7 +291,7 @@ let run = async function() {
         if (!file.name.endsWith(".woff2"))
             continue;
         let family = "/" + file.name;
-        family = family.substring(family.lastIndexOf("/") + 1, family.length - 6);
+        family = family.substring(family.lastIndexOf("/")+1, family.length-6);
         let font = new FontFace(family, file.data);
         await font.load();
         document.fonts.add(font);

core/bus.c

@@ -1,6 +1,10 @@
 /* This file is included into vb.c and cannot be compiled on its own. */
 #ifdef VBAPI
 
+
+
+/***************************** Utility Functions *****************************/
+
 /* Read a data unit from a memory buffer */
 static int32_t busReadMemory(uint8_t *mem, int type) {
 
@@ -28,31 +32,6 @@ static int32_t busReadMemory(uint8_t *mem, int type) {
 
 }
 
-/* Read a data unit from the bus */
-static int32_t busRead(VB *emu, uint32_t address, int type, int debug) {
-
-    /* Force address alignment */
-    address &= ~((uint32_t) TYPE_SIZES[type] - 1);
-
-    /* Process by address range */
-    switch (address >> 24 & 7) {
-        case 0 : return 0; /* VIP */
-        case 1 : debug = debug; return 0; /* VSU */
-        case 2 : return 0; /* Miscellaneous hardware */
-        case 3 : return 0; /* Unmapped */
-        case 4 : return 0; /* Game pak expansion */
-        case 5 : return /* WRAM */
-            busReadMemory(&emu->wram[address & 0xFFFF], type);
-        case 6 : return emu->cart.sram == NULL ? 0 : /* Game pak RAM */
-            busReadMemory(&emu->cart.sram
-                [address & (emu->cart.sramSize - 1)], type);
-        default: return emu->cart.rom  == NULL ? 0 : /* Game pak ROM */
-            busReadMemory(&emu->cart.rom
-                [address & (emu->cart.romSize  - 1)], type);
-    }
-
-}
-
 /* Write a data unit to a memory buffer */
 static void busWriteMemory(uint8_t *mem, int type, int32_t value) {
 
@@ -80,6 +59,35 @@ static void busWriteMemory(uint8_t *mem, int type, int32_t value) {
 
 }
 
+
+
+/***************************** Module Functions ******************************/
+
+/* Read a data unit from the bus */
+static int32_t busRead(VB *emu, uint32_t address, int type, int debug) {
+
+    /* Force address alignment */
+    address &= ~((uint32_t) TYPE_SIZES[type] - 1);
+
+    /* Process by address range */
+    switch (address >> 24 & 7) {
+        case 0 : return 0; /* VIP */
+        case 1 : debug = debug; return 0; /* VSU */
+        case 2 : return 0; /* Miscellaneous hardware */
+        case 3 : return 0; /* Unmapped */
+        case 4 : return 0; /* Game pak expansion */
+        case 5 : return /* WRAM */
+            busReadMemory(&emu->wram[address & 0xFFFF], type);
+        case 6 : return emu->cart.sram == NULL ? 0 : /* Game pak RAM */
+            busReadMemory(&emu->cart.sram
+                [address & (emu->cart.sramSize - 1)], type);
+        default: return emu->cart.rom  == NULL ? 0 : /* Game pak ROM */
+            busReadMemory(&emu->cart.rom
+                [address & (emu->cart.romSize  - 1)], type);
+    }
+
+}
+
 /* Write a data unit to the bus */
 static void busWrite(
     VB *emu, uint32_t address, int type, uint32_t value, int debug) {
@@ -110,4 +118,6 @@ static void busWrite(
 
 }
 
+
+
 #endif /* VBAPI */

core/vb.c

@@ -1,6 +1,7 @@
 #define VBAPI
 
 /* Header includes */
+#include <float.h>
 #include <vb.h>
 
 
@@ -15,7 +16,7 @@ static const uint8_t TYPE_SIZES[] = { 1, 1, 2, 2, 4 };
 /********************************** Macros ***********************************/
 
 /* Sign-extend a value of some number of bits to 32 bits */
-#define SignExtend(v,b) ( (v) | (((v) & 1 << b - 1) ? ~(int32_t)0 << b : 0) )
+#define SignExtend(v,b) ((v) | (((v) & ((1<<(b)) - 1)) ? ~(int32_t)0<<(b) : 0))
 
 
 
@@ -23,11 +24,78 @@ static const uint8_t TYPE_SIZES[] = { 1, 1, 2, 2, 4 };
 
 /* Component includes */
 #include "bus.c"
+#include "cpu.c"
+
+
+
+/***************************** Module Functions ******************************/
+
+/* Process a simulation for some number of clocks */
+static int sysEmulate(VB *emu, uint32_t clocks) {
+    int broke;
+    broke = cpuEmulate(emu, clocks);
+    return broke;
+}
+
+/* Determine the number of clocks before a break condititon could occur */
+static uint32_t sysUntil(VB *emu, uint32_t clocks) {
+    clocks = cpuUntil(emu, clocks);
+    return clocks;
+}
 
 
 
 /******************************* API Functions *******************************/
 
+/* Associate two simulations as peers */
+void vbConnect(VB *emu1, VB *emu2) {
+
+    /* Disconnect any existing link associations */
+    if (emu1->peer != NULL && emu1->peer != emu2)
+        emu1->peer->peer = NULL;
+    if (emu2->peer != NULL && emu2->peer != emu1)
+        emu2->peer->peer = NULL;
+
+    /* Link the two simulations */
+    emu1->peer = emu2;
+    emu2->peer = emu1;
+}
+
+/* Disassociate linked peers */
+void vbDisconnect(VB *emu) {
+    if (emu->peer != NULL)
+        emu->peer->peer = NULL;
+    emu->peer = NULL;
+}
+
+/* Process one or two simulations */
+int vbEmulate(VB *emu1, VB *emu2, uint32_t *clocks) {
+    int      broke; /* The simulation requested an application break */
+    uint32_t until; /* Maximum clocks before a break could happen */
+
+    /* Processing one simulaiton */
+    if (emu2 == NULL) {
+        do {
+            until    = sysUntil  (emu1, *clocks);
+            broke    = sysEmulate(emu1, until  );
+            *clocks -= until;
+        } while (!broke && *clocks > 0);
+    }
+
+    /* Processing two simulations */
+    else {
+        do {
+            until    = sysUntil  (emu1, *clocks);
+            until    = sysUntil  (emu2, until  );
+            broke    = sysEmulate(emu1, until  );
+            broke   |= sysEmulate(emu2, until  );
+            *clocks -= until;
+        } while (!broke && *clocks > 0);
+    }
+
+    return broke;
+}
+
 /* Retrieve the value of PC */
 uint32_t vbGetProgramCounter(VB *emu, int type) {
     switch (type) {
@@ -97,13 +165,23 @@ uint32_t vbGetSystemRegister(VB *emu, int id) {
 /* Prepare a simulation state instance for use */
 void vbInit(VB *emu) {
 
+    /* Breakpoint callbacks */
+    emu->onException = NULL;
+    emu->onExecute   = NULL;
+    emu->onFetch     = NULL;
+    emu->onRead      = NULL;
+    emu->onWrite     = NULL;
+
+    /* System */
+    emu->peer = NULL;
+
     /* Cartridge */
     emu->cart.rom      = NULL;
     emu->cart.romSize  = 0;
     emu->cart.sram     = NULL;
     emu->cart.sramSize = 0;
 
-    /* All others */
+    /* Everything else */
     vbReset(emu);
 }
 
@@ -118,7 +196,7 @@ void vbReset(VB *emu) {
     uint32_t x; /* Iterator */
 
     /* CPU registers */
-    emu->cpu.pc = 0xFFFFFFF0;
+    vbSetProgramCounter(emu,         0xFFFFFFF0);
     vbSetSystemRegister(emu, VB_ECR, 0x0000FFF0);
     vbSetSystemRegister(emu, VB_PSW, 0x00008000);
 
@@ -132,8 +210,19 @@ void vbReset(VB *emu) {
     emu->cpu.fepsw  = 0x00000000;
     emu->cpu.sr29   = 0x00000000;
     emu->cpu.sr31   = 0x00000000;
-    emu->cpu.pcFrom = 0xFFFFFFF0;
+
-    emu->cpu.pcTo   = 0xFFFFFFF0;
+    /* History tracking */
+    emu->cpu.eipcFrom = 0xFFFFFFF0;
+    emu->cpu.eipcTo   = 0xFFFFFFF0;
+    emu->cpu.fepcFrom = 0xFFFFFFF0;
+    emu->cpu.fepcTo   = 0xFFFFFFF0;
+    emu->cpu.pcFrom   = 0xFFFFFFF0;
+    emu->cpu.pcTo     = 0xFFFFFFF0;
+
+    /* Other CPU state */
+    emu->cpu.state = CPU_FETCH;
+    for (x = 0; x < 5; x++)
+        emu->cpu.irq[x] = 0;
 
     /* WRAM (the hardware does not do this) */
     for (x = 0; x < 0x10000; x++)
@@ -142,9 +231,11 @@ void vbReset(VB *emu) {
 
 /* Specify a new value for PC */
 uint32_t vbSetProgramCounter(VB *emu, uint32_t value) {
-    value &= 0xFFFFFFFE;
+    value             &= 0xFFFFFFFE;
-    emu->cpu.pc = value;
+    emu->cpu.fetch     = 0;
-    /* Set stage to fecth=0 */
+    emu->cpu.pc        = value;
+    emu->cpu.state     = CPU_FETCH;
+    emu->cpu.substring = 0;
     return value;
 }
 
@@ -181,42 +272,7 @@ int vbSetSRAM(VB *emu, void *sram, uint32_t size) {
 
 /* Specify a new value for a system register */
 uint32_t vbSetSystemRegister(VB *emu, int id, uint32_t value) {
-    switch (id) {
+    return cpuSetSystemRegister(emu, id, value, 1);
-        case VB_ADTRE: return emu->cpu.adtre = value & 0xFFFFFFFE;
-        case VB_EIPC : return emu->cpu.eipc  = value & 0xFFFFFFFE;
-        case VB_EIPSW: return emu->cpu.eipsw = value & 0x000FF3FF;
-        case VB_FEPC : return emu->cpu.fepc  = value & 0xFFFFFFFE;
-        case VB_FEPSW: return emu->cpu.fepsw = value & 0x000FF3FF;
-        case VB_PIR  : return 0x00005346;
-        case VB_TKCW : return 0x000000E0;
-        case 29      : return emu->cpu.sr29  = value & 0x00000001;
-        case 31      : return emu->cpu.sr31  = value;
-        case VB_CHCW :
-            emu->cpu.chcw.ice = value >> 1 & 1;
-            return value & 0x00000002;
-        case VB_ECR  :
-            emu->cpu.ecr.fecc = value >> 16;
-            emu->cpu.ecr.eicc = value;
-            return value;
-        case VB_PSW  :
-            emu->cpu.psw.i   = value >> 16 & 15;
-            emu->cpu.psw.np  = value >> 15 &  1;
-            emu->cpu.psw.ep  = value >> 14 &  1;
-            emu->cpu.psw.ae  = value >> 13 &  1;
-            emu->cpu.psw.id  = value >> 12 &  1;
-            emu->cpu.psw.fro = value >>  9 &  1;
-            emu->cpu.psw.fiv = value >>  8 &  1;
-            emu->cpu.psw.fzd = value >>  7 &  1;
-            emu->cpu.psw.fov = value >>  6 &  1;
-            emu->cpu.psw.fud = value >>  5 &  1;
-            emu->cpu.psw.fpr = value >>  4 &  1;
-            emu->cpu.psw.cy  = value >>  3 &  1;
-            emu->cpu.psw.ov  = value >>  2 &  1;
-            emu->cpu.psw.s   = value >>  1 &  1;
-            emu->cpu.psw.z   = value       &  1;
-            return value & 0x000FF3FF;
-    }
-    return 0;
 }
 
 /* Write a data unit to the bus */

core/vb.h

@@ -18,11 +18,12 @@ extern "C" {
 /********************************* Constants *********************************/
 
 /* Memory access types */
-#define VB_S8  0
+#define VB_CANCEL -1
-#define VB_U8  1
+#define VB_S8      0
-#define VB_S16 2
+#define VB_U8      1
-#define VB_U16 3
+#define VB_S16     2
-#define VB_S32 4
+#define VB_U16     3
+#define VB_S32     4
 
 /* System register IDs */
 #define VB_ADTRE 25
@@ -45,8 +46,38 @@ extern "C" {
 
 /*********************************** Types ***********************************/
 
-/* Simulation state */
+/* Forward references */
 typedef struct VB VB;
+
+/* Memory access */
+typedef struct {
+    uint32_t address; /* Bus address being accessed */
+    uint32_t clocks;  /* Number of clocks required to complete */
+    int32_t  value;   /* Value read (callback's responsibility) or to write */
+    int8_t   type;    /* Data type of value */
+} VB_ACCESS;
+
+/* CPU instruction */
+typedef struct {
+
+    /* Public fields */
+    uint32_t address; /* Bus address */
+    uint16_t bits[2]; /* Binary instruction code */
+    uint8_t  size;    /* Size in bytes of the instruction */
+
+    /* Implementation fields */
+    int32_t aux[2]; /* Auxiliary storage for CAXI and bit strings */
+    uint8_t id;     /* Internal operation ID */
+} VB_INSTRUCTION;
+
+/* Breakpoint callbacks */
+typedef int (*VB_EXCEPTIONPROC)(VB *, uint16_t);
+typedef int (*VB_EXECUTEPROC  )(VB *, VB_INSTRUCTION *);
+typedef int (*VB_FETCHPROC    )(VB *, int, VB_ACCESS *);
+typedef int (*VB_READPROC     )(VB *, VB_ACCESS *);
+typedef int (*VB_WRITEPROC    )(VB *, VB_ACCESS *);
+
+/* Simulation state */
 struct VB {
 
     /* Game pak */
@@ -101,17 +132,37 @@ struct VB {
 
         /* Other registers */
         uint32_t pc;          /* Program counter */
-        uint32_t pcFrom;      /* Source of most recent jump */
-        uint32_t pcTo;        /* Destination of most recent jump */
         int32_t  program[32]; /* program registers */
 
+        /* History tracking */
+        uint32_t eipcFrom; /* Source of most recent jump */
+        uint32_t eipcTo;   /* Destination of most recent jump */
+        uint32_t fepcFrom; /* Source of most recent jump */
+        uint32_t fepcTo;   /* Destination of most recent jump */
+        uint32_t pcFrom;   /* Source of most recent jump */
+        uint32_t pcTo;     /* Destination of most recent jump */
+
         /* Other fields */
-        uint32_t clocks; /* Clocks until next action */
+        VB_ACCESS      access;    /* Memory access descriptor */
-        uint8_t  fetch;  /* Index of fetch unit */
+        VB_INSTRUCTION inst;      /* Instruction descriptor */
-        uint8_t  state;  /* Operations state */
+        uint8_t        irq[5];    /* Interrupt request lines */
+        uint8_t        busWait;   /* Waiting on a memory access */
+        uint16_t       causeCode; /* Exception cause code */
+        uint32_t       clocks;    /* Clocks until next action */
+        int16_t        fetch;     /* Index of fetch unit */
+        uint8_t        state;     /* Operations state */
+        uint8_t        substring; /* A bit string operation is in progress */
     } cpu;
 
+    /* Breakpoint callbacks */
+    VB_EXCEPTIONPROC onException; /* CPU exception */
+    VB_EXECUTEPROC   onExecute;   /* Instruction execute */
+    VB_FETCHPROC     onFetch;     /* Instruction fetch */
+    VB_READPROC      onRead;      /* Memory read */
+    VB_WRITEPROC     onWrite;     /* Memory write */
+
     /* Other fields */
+    VB     *peer;          /* Communications peer */
     uint8_t wram[0x10000]; /* Main memory */
 };
 
@@ -119,6 +170,9 @@ struct VB {
 
 /**************************** Function Prototypes ****************************/
 
+VBAPI void     vbConnect            (VB *emu1, VB *emu2);
+VBAPI void     vbDisconnect         (VB *emu);
+VBAPI int      vbEmulate            (VB *emu1, VB *emu2, uint32_t *clocks);
 VBAPI uint32_t vbGetProgramCounter  (VB *emu, int type);
 VBAPI int32_t  vbGetProgramRegister (VB *emu, int id);
 VBAPI void*    vbGetROM             (VB *emu, uint32_t *size);

license.txt

@@ -1,4 +1,4 @@
-Copyright (C) 2021 Planet Virtual Boy
+Copyright (C) 2021 Guy Perfect
 
 This software is provided 'as-is', without any express or implied
 warranty.  In no event will the authors be held liable for any damages

makefile

@@ -1,7 +1,7 @@
 .PHONY: help
 help:
 	@echo
-	@echo "Virtual Boy Emulator - September 10, 2021"
+	@echo "Virtual Boy Emulator - September 18, 2021"
 	@echo
 	@echo "Target build environment is any Debian with the following packages:"
 	@echo "  emscripten"