M xywrun.c → xywrun.c

@@ -22,8 +22,8 @@ 
 /* system device */
 #define SYSTEM_STATE 0xff00
 #define SYSTEM_ERROR 0xff01
-#define SYSTEM_SSP 0xff02
-#define SYSTEM_USP 0xff03
+#define SYSTEM_S 0xff02
+#define SYSTEM_U 0xff03
 #define SYSTEM_PAGE 0xff04
 #define SYSTEM_ON_ERROR 0xff05
 
@@ -40,8 +40,8 @@ xyw_byte system_stack[STACK_SIZE];
 xyw_byte user_stack[STACK_SIZE];
 
 //// 1-byte pointers and registers
-xyw_byte *ssp = &xyw_memory[SYSTEM_SSP];
-xyw_byte *usp = &xyw_memory[SYSTEM_USP];
+xyw_byte *s = &xyw_memory[SYSTEM_S];
+xyw_byte *u = &xyw_memory[SYSTEM_U];
 static xyw_byte x_val = 0; // X register storage
 static xyw_byte y_val = 0; // Y register storage
 xyw_byte *x = &x_val;
@@ -78,51 +78,51 @@ //// System stack management
 
 static xyw_word ss_popw()
 {
-    if (*ssp < 2)
+    if (*s < 2)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return -1;
     }
-    xyw_word val = mget(SYSTEM_STACK_START + (*ssp) - 2);
-    mset(SYSTEM_STACK_START + (*ssp) - 2, 0);
-    (*ssp) -= 2;
+    xyw_word val = mget(SYSTEM_STACK_START + (*s) - 2);
+    mset(SYSTEM_STACK_START + (*s) - 2, 0);
+    (*s) -= 2;
     return val;
 }
 
 static void ss_pushw(xyw_word val)
 {
-    if (*ssp > STACK_SIZE - 2)
+    if (*s > STACK_SIZE - 2)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_OVERFLOW;
         return;
     }
-    mset(SYSTEM_STACK_START + *ssp, val);
-    (*ssp) += 2;
+    mset(SYSTEM_STACK_START + *s, val);
+    (*s) += 2;
 }
 
 //// User stack management
 
 static void us_push(xyw_byte val)
 {
-    if (*usp > STACK_SIZE - 1)
+    if (*u > STACK_SIZE - 1)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_OVERFLOW;
         return;
     }
     xyw_dbg(" => %02X\n", val);
-    user_stack[(*usp)++] = val;
+    user_stack[(*u)++] = val;
 }
 
 static void us_pushw(xyw_word val)
 {
-    if (*usp > STACK_SIZE - 2)
+    if (*u > STACK_SIZE - 2)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_OVERFLOW;
         return;
     }
-    mset(USER_STACK_START + *usp, val);
+    mset(USER_STACK_START + *u, val);
     xyw_dbg(" => %04X\n", val);
-    (*usp) += 2;
+    (*u) += 2;
 }
 
 //// Instructions
@@ -149,73 +149,73 @@ static void PSHyw() { us_pushw(*yw); }
 
 static xyw_byte POP()
 {
-    if (*usp < 1)
+    if (*u < 1)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return -1;
     }
-    xyw_byte val = user_stack[--(*usp)];
-    user_stack[*usp] = 0;
+    xyw_byte val = user_stack[--(*u)];
+    user_stack[*u] = 0;
     return val;
 }
 
 static xyw_word POPw()
 {
-    if (*usp < 2)
+    if (*u < 2)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return -1;
     }
-    xyw_word val = mget(USER_STACK_START + (*usp) - 2);
-    mset(USER_STACK_START + (*usp) - 2, 0);
-    (*usp) -= 2;
+    xyw_word val = mget(USER_STACK_START + (*u) - 2);
+    mset(USER_STACK_START + (*u) - 2, 0);
+    (*u) -= 2;
     return val;
 }
 
 static void POPx()
 {
-    if (*usp < 1)
+    if (*u < 1)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return;
     }
-    *x = user_stack[--(*usp)];
-    user_stack[*usp] = 0;
+    *x = user_stack[--(*u)];
+    user_stack[*u] = 0;
 }
 
 static void POPy()
 {
-    if (*usp < 1)
+    if (*u < 1)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return;
     }
-    *y = user_stack[--(*usp)];
-    user_stack[*usp] = 0;
+    *y = user_stack[--(*u)];
+    user_stack[*u] = 0;
 }
 
 static void POPxw()
 {
-    if (*usp < 2)
+    if (*u < 2)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return;
     }
-    *xw = mget(USER_STACK_START + (*usp) - 2);
-    mset(USER_STACK_START + (*usp) - 2, 0);
-    (*usp) -= 2;
+    *xw = mget(USER_STACK_START + (*u) - 2);
+    mset(USER_STACK_START + (*u) - 2, 0);
+    (*u) -= 2;
 }
 
 static void POPyw()
 {
-    if (*usp < 2)
+    if (*u < 2)
     {
         xyw_memory[SYSTEM_ERROR] = XYW_ERROR_STACK_UNDERFLOW;
         return;
     }
-    *yw = mget(USER_STACK_START + (*usp) - 2);
-    mset(USER_STACK_START + (*usp) - 2, 0);
-    (*usp) -= 2;
+    *yw = mget(USER_STACK_START + (*u) - 2);
+    mset(USER_STACK_START + (*u) - 2, 0);
+    (*u) -= 2;
 }
 
 static void LDRx() { us_push(xyw_memory[*x]); }