diff --git a/Port/80251/port_80251.h b/Port/80251/port_80251.h
index d135c5cb..eb204cae 100644
--- a/Port/80251/port_80251.h
+++ b/Port/80251/port_80251.h
@@ -292,4 +292,8 @@ do{ \
 #define mxResumeIRQ()   mx_resume_irq()
 
 
+/* 内存访问屏障 */
+#define __mx_MMB()
+
+
 #endif