diff --git a/grc/demapping/gsm_sdcch8_demapper.xml b/grc/demapping/gsm_sdcch8_demapper.xml
index c81032a..7507065 100644
--- a/grc/demapping/gsm_sdcch8_demapper.xml
+++ b/grc/demapping/gsm_sdcch8_demapper.xml
@@ -1,61 +1,30 @@
-<?xml version="1.0"?>
 <block>
   <name>SDCCH/8 demapper</name>
   <key>gsm_sdcch8_demapper</key>
+  <category></category>
   <import>import grgsm</import>
-  <make>grgsm.universal_ctrl_chans_demapper($timeslot_nr, $downlink_starts_fn_mod51, $downlink_channel_types, $uplink_starts_fn_mod51, $uplink_channel_types)</make>
-
+  <make>grgsm.gsm_sdcch8_demapper(
+    timeslot_nr=$timeslot_nr,
+)</make>
+  <callback>set_timeslot_nr($timeslot_nr)</callback>
   <param>
-    <name>Timeslot</name>
+    <name>timeslot_nr</name>
     <key>timeslot_nr</key>
     <value>1</value>
-    <type>int</type>
-    <hide>none</hide>
+    <type>raw</type>
   </param>
-
-  <param>
-    <name>downlink_starts_fn_mod51</name>
-    <key>downlink_starts_fn_mod51</key>
-    <value>[0,4,8,12,16,20,24,28,32,36,40,44]</value>
-    <type>int_vector</type>
-    <hide>all</hide>
-  </param>
-
-  <param>
-    <name>downlink_channel_types</name>
-    <key>downlink_channel_types</key>
-    <value>[8,8,8,8,8,8,8,8,136,136,136,136]</value>
-    <type>int_vector</type>
-    <hide>all</hide>
-  </param>
-
-  <param>
-    <name>uplink_starts_fn_mod51</name>
-    <key>uplink_starts_fn_mod51</key>
-    <value>[15,19,23,27,31,35,39,43,47,0,4,8]</value>
-    <type>int_vector</type>
-    <hide>all</hide>
-  </param>
-
-  <param>
-    <name>uplink_channel_types</name>
-    <key>uplink_channel_types</key>
-    <value>[8,8,8,8,8,8,8,8,136,136,136,136]</value>
-    <type>int_vector</type>
-    <hide>all</hide>
-  </param>
-
   <sink>
     <name>bursts</name>
     <type>message</type>
+    <optional>1</optional>
   </sink>
   <source>
     <name>bursts</name>
     <type>message</type>
+    <optional>1</optional>
   </source>
-  
-  <doc>
-      Demapper for SDCCH/8 + SACCH/C8 control channels.
-      This corresponds to channel combination vii specified in GSM 05.02, section 6.4
-  </doc>
+  <doc>Piotr Krysik
+Demapper for SDCCH/8 + SACCH/C8 control channels. This corresponds to channel combination vii specified in GSM 05.02, section 6.4
+</doc>
+  <grc_source>gr-gsm/hier_blocks/demapping/gsm_sdcch8_demapper.grc</grc_source>
 </block>