diff --git a/src/ebusd/busloop.cpp b/src/ebusd/busloop.cpp
index f0f333fb..f4484787 100644
--- a/src/ebusd/busloop.cpp
+++ b/src/ebusd/busloop.cpp
@@ -307,38 +307,56 @@ void BusLoop::collectCycData(const int numRecv)
 
 void BusLoop::analyseCycData()
 {
-	//TODO check the input data for validity
+	int lenMaster = m_sstr[4];
+	SymbolString master;
 
-	static bool skipfirst = false;
+	for (int i = 0; i < 5+lenMaster; i++)
+		master.push_back(m_sstr[i], true , true);
 
-	if (skipfirst == true) {
-		L.log(cyc, trace, "%s", m_sstr.getDataStr().c_str());
-
-		int index = m_commands->storeCycData(m_sstr.getDataStr());
-
-		if (index == -1) {
-			L.log(cyc, debug, " command not found");
-		}
-		else if (index == -2) {
-			L.log(cyc, debug, " no commands defined");
-		}
-		else if (index == -3) {
-			L.log(cyc, debug, " search skipped - string too short");
-		}
-		else {
-			string tmp;
-			tmp += (*m_commands)[index][1];
-			tmp += " ";
-			tmp += (*m_commands)[index][2];
-			L.log(cyc, event, " cycle   [%4d] %s", index, tmp.c_str());
-		}
-
-		// collect Slave address
-		if (index != -3)
-			collectSlave();
+	if (m_sstr[5+lenMaster] != master.getCRC()) {
+		L.log(cyc, trace, "ERR_CYC_CRC_M %s - %02x %02x", master.getDataStr().c_str(), m_sstr[5+lenMaster], master.getCRC());
+		return;
 	}
-	else
-		skipfirst = true;
+
+	if (m_sstr[1] != BROADCAST || isMaster(m_sstr[1]) == false) {
+		int lenSlave = m_sstr[5+lenMaster+2];
+		SymbolString slave;
+
+		for (int i = 5+lenMaster+2; i < 5+lenMaster+3+lenSlave; i++)
+			slave.push_back(m_sstr[i], true , true);
+
+		if (m_sstr[5+lenMaster+3+lenSlave] != slave.getCRC()) {
+			L.log(cyc, trace, "ERR_CYC_CRC_S %s - %02x %02x", slave.getDataStr().c_str(), m_sstr[5+lenMaster+3+lenSlave], slave.getCRC());
+			return;
+		}
+	}
+
+
+	L.log(cyc, trace, "%s", m_sstr.getDataStr().c_str());
+
+	int index = m_commands->storeCycData(m_sstr.getDataStr());
+
+	if (index == -1) {
+		L.log(cyc, debug, " command not found");
+	}
+	else if (index == -2) {
+		L.log(cyc, debug, " no commands defined");
+	}
+	else if (index == -3) {
+		L.log(cyc, debug, " search skipped - string too short");
+	}
+	else {
+		string tmp;
+		tmp += (*m_commands)[index][1];
+		tmp += " ";
+		tmp += (*m_commands)[index][2];
+		L.log(cyc, event, " cycle   [%4d] %s", index, tmp.c_str());
+	}
+
+	// collect Slave address
+	if (index != -3)
+		collectSlave();
+
 }
 
 void BusLoop::collectSlave()