improve vectors start address calculation

retroenv · Jun 1, 2024 · 6172911 · 6172911
1 parent 8d9a04b
commit 6172911
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Showing 4 changed files with 17 additions and 13 deletions.
diff --git a/internal/assembler/asm6/file.go b/internal/assembler/asm6/file.go
@@ -185,9 +185,7 @@ func (f FileWriter) writeVectors() error {
 		return nil
 	}
 
-	vectorStart := int(f.app.CodeBaseAddress) + f.app.PrgSize() - 6
-	addr := fmt.Sprintf("$%04X", vectorStart)
-
+	addr := fmt.Sprintf("$%04X", f.app.VectorsStartAddress)
 	if err := f.writeSegment(addr); err != nil {
 		return err
 	}

diff --git a/internal/assembler/nesasm/file.go b/internal/assembler/nesasm/file.go
@@ -164,8 +164,7 @@ func (f FileWriter) writeVectors() error {
 		return nil
 	}
 
-	vectorStart := int(f.app.CodeBaseAddress) + f.app.PrgSize() - 6
-	if _, err := fmt.Fprintf(f.mainWriter, "\n .org $%04X\n", vectorStart); err != nil {
+	if _, err := fmt.Fprintf(f.mainWriter, "\n .org $%04X\n", f.app.VectorsStartAddress); err != nil {
 		return fmt.Errorf("writing segment: %w", err)
 	}
 

diff --git a/internal/disasm.go b/internal/disasm.go
@@ -50,7 +50,8 @@ type Disasm struct {
 	handlers                program.Handlers
 	noUnofficialInstruction bool // enable for assemblers that do not support unofficial opcodes
 
-	codeBaseAddress uint16 // codebase address of the cartridge, as it can be different from 0x8000
+	codeBaseAddress     uint16 // codebase address of the cartridge, as it can be different from 0x8000
+	vectorsStartAddress uint16
 
 	constants     map[uint16]constTranslation
 	usedConstants map[uint16]constTranslation
@@ -250,12 +251,15 @@ func (dis *Disasm) initializeIrqHandlers() {
 func (dis *Disasm) calculateCodeBaseAddress(resetHandler uint16) {
 	halfPrg := len(dis.cart.PRG) % 0x8000
 	dis.codeBaseAddress = uint16(0x8000 + halfPrg)
+	dis.vectorsStartAddress = uint16(irqStartAddress)
 
 	// fix up calculated code base address for half sized PRG ROMs that have a different
 	// code base address configured in the assembler, like "M.U.S.C.L.E."
 	if resetHandler < dis.codeBaseAddress {
 		dis.codeBaseAddress = nes.CodeBaseAddress
+		dis.vectorsStartAddress -= uint16(halfPrg)
 	}
+
 	dis.logger.Debug("Code base address",
 		log.String("address", fmt.Sprintf("0x%04X", dis.codeBaseAddress)))
 }
@@ -270,6 +274,7 @@ func (dis *Disasm) CodeBaseAddress() uint16 {
 func (dis *Disasm) convertToProgram() (*program.Program, error) {
 	app := program.New(dis.cart)
 	app.CodeBaseAddress = dis.codeBaseAddress
+	app.VectorsStartAddress = dis.vectorsStartAddress
 	app.Handlers = dis.handlers
 
 	for _, bnk := range dis.banks {

diff --git a/internal/program/program.go b/internal/program/program.go
@@ -51,13 +51,15 @@ type Program struct {
 	RAM     byte       // PRG-RAM offsets
 	Trainer []byte
 
-	CodeBaseAddress uint16
-	Checksums       Checksums
-	Handlers        Handlers
-	Battery         byte
-	Mirror          cartridge.MirrorMode
-	Mapper          byte
-	VideoFormat     byte
+	CodeBaseAddress     uint16
+	VectorsStartAddress uint16
+
+	Checksums   Checksums
+	Handlers    Handlers
+	Battery     byte
+	Mirror      cartridge.MirrorMode
+	Mapper      byte
+	VideoFormat byte
 
 	// keep constants and variables in the banks and global in the app to let the chosen assembler decide
 	// how to output them