A examples/on-error.xyw

@@ -0,0 +1,31 @@ 
+.include "devices.xyw" 
+
+; register on error handler
+on_error system.on_error STW
+
+; main program
+$10 $0 DIV
+end JMPw
+
+; on error handler
+.label on_error
+    system.error $1 EQU on_error.print JCNw
+    RTS
+    .label on_error.print
+        ;error print JSRw
+        $55 $fe00 STBw
+        $0 system.error STB
+    RTS
+
+; a16 --
+; printing subroutine
+.label print
+  POPxw
+  .label print.loop
+    LDBxw terminal.output STB
+    INCxw LDBxw print.loop JCNw
+    RTS
+
+.label error
+.string "Error: Division by zero.\n"
+.label end

M xywrun.c → xywrun.c

@@ -43,12 +43,17 @@ #endif
 typedef enum
 {
     XYW_ERROR_NONE = 0,
+    XYW_ERROR_DIVISION_BY_ZERO,
     XYW_ERROR_INVALID_INSTRUCTION,
     XYW_ERROR_STACK_UNDERFLOW,
     XYW_ERROR_STACK_OVERFLOW,
     XYW_ERROR_DEVICE_UNAVAILABLE,
     XYW_ERROR_INVALID_DEVICE_PORT
 } xyw_error;
+
+#define SYSTEM_STATE_RUNNING 0x01
+#define SYSTEM_STATE_DEBUG 0x40
+#define SYSTEM_STATE_ERROR 0x80
 
 /// Main memory and stacks
 xyw_byte xyw_memory[MEMORY_SIZE];
@@ -293,8 +298,36 @@ //// Returns 1 on success, 0 on error
 int xyw_eval(xyw_word start_pc)
 {
     *pc = start_pc;
-    while (xyw_memory[SYSTEM_STATE] && *pc < SYSTEM_MEMORY_START)
+    if (xyw_memory[SYSTEM_STATE] & xyw_debug)
     {
+        xyw_memory[SYSTEM_STATE] |= SYSTEM_STATE_DEBUG;
+    }
+
+    while ((xyw_memory[SYSTEM_STATE] & SYSTEM_STATE_RUNNING) && *pc < SYSTEM_MEMORY_START)
+    {
+        printf("ERROR: %d - State: %04X\n", xyw_memory[SYSTEM_ERROR], xyw_memory[SYSTEM_STATE]);
+        if (xyw_memory[SYSTEM_ERROR] == XYW_ERROR_NONE)
+        {
+            // Clear error state if no error
+            xyw_memory[SYSTEM_STATE] &= ~SYSTEM_STATE_ERROR;
+        }
+        if (xyw_memory[SYSTEM_ERROR] != XYW_ERROR_NONE && !(xyw_memory[SYSTEM_STATE] & SYSTEM_STATE_ERROR))
+        {
+            // An error has occurred, update state
+            xyw_memory[SYSTEM_STATE] |= SYSTEM_STATE_ERROR;
+            xyw_word on_error_handler = XYW_PEEKW(&xyw_memory[SYSTEM_ON_ERROR]);
+            // If an error handler is set, jump to it
+            if (on_error_handler != 0)
+            {
+                ss_pushw(*pc);
+                *pc = on_error_handler;
+            }
+            else
+            {
+                // No error handler, halt execution
+                return xyw_memory[SYSTEM_ERROR];
+            }
+        }
         xyw_dbg("PC: %04X -> %02X (%s) [U:%02X|S:%02X|X:%02X|Y:%02X|XW:%04X|YW:%04X]\n", *pc, xyw_memory[*pc], xyw_instructions[xyw_memory[*pc] & 0x1F], *u, *s, *x, *y, *xw, *yw);
         switch (xyw_memory[*pc])
         {
@@ -325,7 +358,7 @@ /* SHR */ OPC_SR1r(0x0B, xyw_byte val = us_pop(); SET(ARGX >> val); SET(ARGY >> val); );
             /* ADD */ OPC_SR2(0x0C, PUSH(a + b));
             /* SUB */ OPC_SR2(0x0D, PUSH(a - b));
             /* MUL */ OPC_SR2(0x0E, PUSH(a * b));
-            /* DIV */ OPC_SR2(0x0F, PUSH(a % b); PUSH(a / b));
+            /* DIV */ OPC_SR2(0x0F, printf("b: %d\n", b); if (b) { PUSH(a % b); PUSH(a / b); } else { xyw_memory[SYSTEM_ERROR] = XYW_ERROR_DIVISION_BY_ZERO; } );
             /* EQU */ OPC_SR2(0x10, PUSH(a == b));
             /* NEQ */ OPC_SR2(0x11, PUSH(a != b));
             /* GTH */ OPC_SR2(0x12, PUSH(a > b));
@@ -341,7 +374,7 @@ /* DUP */ OPC_SR1r(0x19, SETX(READ(USER_STACK_START + (*u) - (w ? 2 : 1))); SETY(READ(USER_STACK_START + (*u) - (w ? 2 : 1))); );
             /* OVR */ OPC_SR2(0x1A, PUSH(b); PUSH(a); PUSH(b));
             /* ROT */ OPC_SR2(0x1B, PUSH(b); PUSH(POP()); PUSH(a));
             /* JMP */ OPC_SR1(0x1C, , *pc = ADDR(ARG)-1;);
-            /* JCN */ OPC_SR1(0x1D, xyw_word addr = ADDR(ARG), if (us_pop()) { *pc = addr-1; });
+            /* JCN */ OPC_SR1(0x1D, , xyw_word addr = ADDR(ARG); xyw_byte cond = us_pop(); printf("JCN to %04X if %d\n", addr, cond); if (cond) { *pc = addr-1; });
             /* JSR */ OPC_SR1(0x1E, xyw_word addr = ADDR(ARG),  ss_pushw(*pc+1); *pc = addr-1;);
             /* RTS */ case 0x1F: *pc = ss_popw()-1; break;
             // clang-format on
@@ -370,7 +403,7 @@ return -1;
     }
     xyw_dbg("Loaded %zu bytes into memory\n", bytes_read);
     fclose(fp);
-    xyw_memory[SYSTEM_STATE] = 1;
+    xyw_memory[SYSTEM_STATE] |= SYSTEM_STATE_RUNNING;
     // Initialize devices
     for (int i = 0; i < XYW_TOTAL_DEVICES; i++)
     {
@@ -391,7 +424,7 @@ // If terminal vector is set, enter stdin reading loop
         if (terminal_vector)
         {
             xyw_dbg("terminal.on_keypress vector set to %04X, entering input loop\n", terminal_vector);
-            while (xyw_memory[SYSTEM_STATE])
+            while (xyw_memory[SYSTEM_STATE] & SYSTEM_STATE_RUNNING)
             {
                 int c = getch();
                 // if CTRL+C or CTRL+D is pressed, exit