diff --git a/bstrd/bscache.py b/bstrd/bscache.py
index 3cab89d..b220657 100644
--- a/bstrd/bscache.py
+++ b/bstrd/bscache.py
@@ -26,14 +26,18 @@ class BSCache:
 
 
     def run(self, running):
+        timeout_counter = 0
         configs = self.channels.values()
         with source(channels=configs, receive_timeout=self.timeout) as src:
             while running.is_set():
                 msg = src.receive()
                 if msg is None:
+                    timeout_counter += 1
+                    print("receive timed out", timeout_counter)
                     continue
                 data = repack(msg)
                 if data:
+                    data["toc"] = timeout_counter
                     yield data
 
 
@@ -42,7 +46,7 @@ class BSCache:
 
 
     def get_var(self, name, modulo=None, offset=None):
-        if name != "pid" and name not in self.channels:
+        if name not in ["pid", "toc"] and name not in self.channels:
             if not is_available(name):
                 raise ValueError(f"channel {name} is not available")
             cfg = make_channel_config(name, modulo, offset)