movable sp for sim65

src/sim65/main.c

@@ -132,11 +132,12 @@ static void OptQuitXIns (const char* Opt attribute ((unused)),
     MaxCycles = strtoul(Arg, NULL, 0);
 }
 
-static void ReadProgramFile (void)
+static unsigned char ReadProgramFile (void)
 /* Load program into memory */
 {
     int Val;
     unsigned Addr = 0x0200;
+    unsigned char SPAddr = 0x0000;
 
     /* Open the file */
     FILE* F = fopen (ProgramFile, "rb");
@@ -152,6 +153,11 @@ static void ReadProgramFile (void)
         CPU = Val;
     }
 
+    /* Get the address of sp from the file header */
+    if ((Val = fgetc(F)) != EOF) {
+        SPAddr = Val;
+    }
+
     /* Read the file body into memory */
     while ((Val = fgetc(F)) != EOF) {
         if (Addr == 0xFF00) {
@@ -169,6 +175,8 @@ static void ReadProgramFile (void)
     fclose (F);
 
     Print (stderr, 1, "Loaded '%s' at $0200-$%04X\n", ProgramFile, Addr - 1);
+
+    return SPAddr;
 }
 
 
@@ -184,6 +192,7 @@ int main (int argc, char* argv[])
     };
 
     unsigned I;
+    unsigned char SPAddr;
 
     /* Initialize the cmdline module */
     InitCmdLine (&argc, &argv, "sim65");
@@ -243,11 +252,11 @@ int main (int argc, char* argv[])
         AbEnd ("No program file");
     }
 
-    ParaVirtInit (I);
-
     MemInit ();
 
-    ReadProgramFile ();
+    SPAddr = ReadProgramFile ();
+
+    ParaVirtInit (I, SPAddr);
 
     Reset ();
 

src/sim65/paravirt.c

@@ -77,6 +77,7 @@
 typedef void (*PVFunc) (CPURegs* Regs);
 
 static unsigned ArgStart;
+static unsigned char SPAddr;
 
 
 
@@ -120,9 +121,9 @@ static unsigned char Pop (CPURegs* Regs)
 
 static unsigned PopParam (unsigned char Incr)
 {
-    unsigned SP = MemReadZPWord (0x00);
+    unsigned SP = MemReadZPWord (SPAddr);
     unsigned Val = MemReadWord (SP);
-    MemWriteWord (0x0000, SP + Incr);
+    MemWriteWord (SPAddr, SP + Incr);
     return Val;
 }
 
@@ -132,7 +133,7 @@ static void PVArgs (CPURegs* Regs)
 {
     unsigned ArgC = ArgCount - ArgStart;
     unsigned ArgV = GetAX (Regs);
-    unsigned SP   = MemReadZPWord (0x00);
+    unsigned SP   = MemReadZPWord (SPAddr);
     unsigned Args = SP - (ArgC + 1) * 2;
 
     Print (stderr, 2, "PVArgs ($%04X)\n", ArgV);
@@ -152,9 +153,9 @@ static void PVArgs (CPURegs* Regs)
         MemWriteWord (Args, SP);
         Args += 2;
     }
-    MemWriteWord (Args, 0x0000);
+    MemWriteWord (Args, SPAddr);
 
-    MemWriteWord (0x0000, SP);
+    MemWriteWord (SPAddr, SP);
     SetAX (Regs, ArgC);
 }
 
@@ -313,10 +314,11 @@ static const PVFunc Hooks[] = {
 
 
 
-void ParaVirtInit (unsigned aArgStart)
+void ParaVirtInit (unsigned aArgStart, unsigned char aSPAddr)
 /* Initialize the paravirtualization subsystem */
 {
     ArgStart = aArgStart;
+    SPAddr = aSPAddr;
 };
 
 

src/sim65/paravirt.h

@@ -44,7 +44,7 @@
 
 
 
-void ParaVirtInit (unsigned aArgStart);
+void ParaVirtInit (unsigned aArgStart, unsigned char aSPAddr);
 /* Initialize the paravirtualization subsystem */
 
 void ParaVirtHooks (CPURegs* Regs);