diff --git a/utils/rst28.inc b/utils/rst28.inc
new file mode 100644
index 0000000..81875e1
--- /dev/null
+++ b/utils/rst28.inc
@@ -0,0 +1,17 @@
+; rst28.inc
+;
+; SPDX-FileCopyrightText: Copyright (C) 2019, 2021 Antonio Villena
+;
+; SPDX-License-Identifier: GPL-3.0-only
+
+; Compatible compilers:
+;   SJAsmPlus, <https://github.com/sjasmplus/sjasmplus/>
+
+                include zxuno.def
+
+rst28           ld      bc, zxuno_port + $100
+                pop     hl
+                outi
+                ld      b, (zxuno_port >> 8)+2
+                outi
+                jp      (hl)