diff --git a/bonn1master.json b/bonn1master.json
index f1242e0..659f36d 100644
--- a/bonn1master.json
+++ b/bonn1master.json
@@ -5,6 +5,7 @@
     "base": "master",
     "core_addr": "10.0.16.100",
     "vendor": "QUARTIQ",
+    "ext_ref_frequency": 10e6,
     "peripherals": [
         {
             "type": "dio",