diff --git a/internal/compiler/funchandler.go b/internal/compiler/funchandler.go
index ee254e5..6920775 100644
--- a/internal/compiler/funchandler.go
+++ b/internal/compiler/funchandler.go
@@ -272,25 +272,57 @@ func (fh *FunctionHandler) HandleFuncCall(line preproc.Line) ([]string, error) {
 	for i, arg := range callArgs {
 		param := funcDecl.Params[i]
 
-		// Handle different argument types
+		// Handle special cases first
 		if strings.HasPrefix(arg, "@") {
 			// Label reference: @labelname
 			if err := fh.processLabelArg(arg, param, funcName, line, &inAssigns); err != nil {
 				return nil, err
 			}
-		} else if strings.HasPrefix(arg, "\"") && strings.HasSuffix(arg, "\"") {
+			continue
+		}
+
+		if strings.HasPrefix(arg, "\"") && strings.HasSuffix(arg, "\"") {
 			// String constant
 			if err := fh.processStringArg(arg, param, funcName, line, pragmaSet, &inAssigns); err != nil {
 				return nil, err
 			}
-		} else if sym := fh.symTable.Lookup(arg, fh.currentFuncs); sym != nil {
-			// Variable reference
+			continue
+		}
+
+		// Use ParseOperandParam for variables, constants, and expressions
+		constLookup := func(name string) (int64, bool) {
+			if sym := fh.symTable.Lookup(name, fh.currentFuncs); sym != nil && sym.IsConst() {
+				return int64(sym.Value), true
+			}
+			return 0, false
+		}
+
+		_, _, value, isVar, err := ParseOperandParam(
+			arg, fh.symTable, fh.currentFuncs, constLookup)
+		if err != nil {
+			return nil, fmt.Errorf("%s:%d: CALL %s arg %d (%q): %w",
+				line.Filename, line.LineNo, funcName, i+1, arg, err)
+		}
+
+		// Out/IO parameters must be writable variables
+		if param.Direction.Has(DirOut) && !isVar {
+			return nil, fmt.Errorf("%s:%d: CALL %s: cannot pass constant/expression to out/io parameter %q",
+				line.Filename, line.LineNo, funcName, param.Symbol.Name)
+		}
+
+		if isVar {
+			// Variable - get full symbol for type checking
+			sym := fh.symTable.Lookup(arg, fh.currentFuncs)
+			if sym == nil {
+				return nil, fmt.Errorf("%s:%d: CALL %s: internal error - variable %q not found",
+					line.Filename, line.LineNo, funcName, arg)
+			}
 			if err := fh.processVarArg(sym, param, funcName, line, &inAssigns, &outAssigns); err != nil {
 				return nil, err
 			}
 		} else {
-			// Numeric constant
-			if err := fh.processConstArg(arg, param, funcName, line, &inAssigns); err != nil {
+			// Constant or expression result
+			if err := fh.processConstValue(value, param, funcName, line, &inAssigns); err != nil {
 				return nil, err
 			}
 		}
@@ -439,6 +471,34 @@ func (fh *FunctionHandler) processConstArg(arg string, param *FuncParam, funcNam
 	return nil
 }
 
+// processConstValue handles pre-computed constant/expression values
+// Used after ParseOperandParam has already validated and computed the value
+func (fh *FunctionHandler) processConstValue(value uint16, param *FuncParam, funcName string, line preproc.Line, inAssigns *[]string) error {
+	// Verify value fits in parameter type
+	if param.Symbol.IsByte() && value > 255 {
+		return fmt.Errorf("%s:%d: CALL %s: value %d out of byte range for parameter %q",
+			line.Filename, line.LineNo, funcName, value, param.Symbol.Name)
+	}
+
+	lowByte := uint8(value & 0xFF)
+	highByte := uint8((value >> 8) & 0xFF)
+
+	*inAssigns = append(*inAssigns,
+		fmt.Sprintf("  lda #%d", lowByte),
+		fmt.Sprintf("  sta %s", param.Symbol.FullName()),
+	)
+
+	if param.Symbol.IsWord() {
+		// Optimize: only reload A if high byte differs
+		if highByte != lowByte {
+			*inAssigns = append(*inAssigns, fmt.Sprintf("  lda #%d", highByte))
+		}
+		*inAssigns = append(*inAssigns, fmt.Sprintf("  sta %s+1", param.Symbol.FullName()))
+	}
+
+	return nil
+}
+
 // parseImplicitDecl parses {BYTE varname} or {WORD varname} and adds to symbol table
 func (fh *FunctionHandler) parseImplicitDecl(decl string, funcName string) error {
 	parts := strings.Fields(decl)