diff --git a/src/hwapi.cpp b/src/hwapi.cpp
index 599e7b7..20bc059 100644
--- a/src/hwapi.cpp
+++ b/src/hwapi.cpp
@@ -22,11 +22,12 @@
 #include "hwapi.h"
 #include "download_thread.h"
 #include "reporting_thread.h"
+#include "shared_mem_buffer.h"
 
 #include <cstring>
 #include <QThread>
 #include <QDebug>
-
+#include <QApplication>
 
 static uint32_t hwapi_lastStartAmount;
 static uint32_t hwapi_lastTotalAmount;
@@ -58,6 +59,9 @@ hwapi::hwapi(QWidget *parent) : QObject(parent)
         qCritical() << "Creating/attaching shared memory failed";
     }
 
+    Q_ASSERT_X(sizeof(SharedMem) != m_sharedMem->size(),
+               "compare sizes", "sizes different");
+
     //if (shdMem_firstUse())        // für Master raus
 //    {
 
@@ -67,7 +71,7 @@ hwapi::hwapi(QWidget *parent) : QObject(parent)
 #error "SLAVE LIB COMPILED INTO MASTER"
 #endif
 
-        myDatif = new T_datif();    // für die  CAslave-Lib auskommentieren!
+        myDatif = new T_datif(this);    // für die  CAslave-Lib auskommentieren!
 
 #endif
 
@@ -4412,6 +4416,7 @@ QObject const *hwapi::getAPI() {
 }
 
 bool hwapi::dcDownloadRequest(QString const &dcFileToDownload) const {
+    // called by worker-thread (see atbupdatetool)
     SharedMem *data = SharedMem::getData();
     if (!data) {
         return false;
@@ -4435,9 +4440,15 @@ bool hwapi::dcDownloadRequest(QString const &dcFileToDownload) const {
 }
 
 bool hwapi::dcDownloadRequested() const {
-    SharedMem const *data = SharedMem::getData();
-    // should be false at entry
-    return data ? data->m_downLoadDC.m_requested.load() : false;
+    SharedMem *data = SharedMem::getData();
+    Q_ASSERT_X(data != nullptr, "check", "pointer invalid");
+    Q_ASSERT_X((void *)data != m_sharedMem->data(), "compare pointers", "pointers different");
+    Q_ASSERT_X(sizeof(*data) != m_sharedMem->size(), "compare sizes", "sizes different");
+
+    // called by download-thread
+    // 1: true at entry: reset atomically to false
+    // 2: false at entry: no change
+    return data ? data->m_downLoadDC.m_requested.exchange(false) : false;
 }
 
 bool hwapi::dcDownloadResetRequest() const {
@@ -4449,13 +4460,11 @@ bool hwapi::dcDownloadResetRequest() const {
 }
 
 bool hwapi::dcDownloadRequestAck() const {
+    // called by download-thread
     SharedMem *data = SharedMem::getData();
     if (data) {
-        if (data->m_downLoadDC.m_requested) {
-            data->m_downLoadDC.m_requested = false;
-            data->m_downLoadDC.m_running = true;
-            data->m_downLoadDC.m_finished = false;
-        }
+        data->m_downLoadDC.m_running = true;
+        data->m_downLoadDC.m_finished = false;
     }
     return false;
 }
@@ -4465,14 +4474,16 @@ bool hwapi::dcDownloadRunning() const {
     if (data) {
         int cnt = 10;
         while (--cnt > 0) {
-            bool running = data->m_downLoadDC.m_running.load();
-            bool finished = data->m_downLoadDC.m_finished.load();
-            if (!running || finished) {
-                if (cnt < 3) {
-                    qCritical() << "DOWNLOAD THREAD NOT RUNNING" << running << finished;
-                }
-                QThread::msleep(500);
-            } else break;
+            bool running = data->m_downLoadDC.m_running;
+            bool finished = data->m_downLoadDC.m_finished;
+            if ((running == true) && (finished == false)) {
+                // see dcDownloadRequestAck()
+                break;
+            }
+            if (cnt < 3) {
+                qCritical() << "DOWNLOAD THREAD NOT RUNNING" << running << finished;
+            }
+            QThread::msleep(500);
         }
         // qCritical() << "DOWNLOAD RUNNING" << cnt << (cnt > 0);
         return (cnt > 0);
@@ -4481,18 +4492,16 @@ bool hwapi::dcDownloadRunning() const {
 }
 
 void hwapi::dcDownloadThreadFinalize(DownloadThread *dthread) {
-    delete dthread;
+    Q_UNUSED(dthread);
+    // delete dthread;
     m_downloadThread = nullptr;
 }
 
 bool hwapi::dcDownloadFinished() {
-    SharedMem const *data = SharedMem::getDataConst();
-    if (data) {
-        int cnt = 10;
-        while ((--cnt > 0) &&
-               ((data->m_downLoadDC.m_running.load() == true) &&
-                (data->m_downLoadDC.m_finished.load() == false))) {
-            QThread::sleep(1);
+    int cnt = 10;
+    while (dcDownloadRunning()) {
+        if (--cnt == 0) {
+            return false;
         }
 
         //if (cnt > 0) {
@@ -4501,12 +4510,13 @@ bool hwapi::dcDownloadFinished() {
         //    return true;
         //}
     }
-    return false;
+    return true;
 }
 
 // download thread
 
 bool hwapi::dcDownloadThreadStart() {
+    // called by timer in datIf.cpp: T_datif::datif_cycleSend()
     m_downloadThread = new DownloadThread(this);
     if (m_downloadThread) {
         m_downloadThread->start();
@@ -4569,7 +4579,9 @@ void hwapi::dcDownloadReportThreadQuit() {
 }
 
 bool hwapi::dcDownloadReportThreadFinished() const {
-    return m_reportingThread ? m_reportingThread->isFinished() : false;
+    // if the pointer to the underlying c++-object is not valid, the thread
+    // counts as finished
+    return m_reportingThread ? m_reportingThread->isFinished() : true;
 }
 
 bool hwapi::dcDownloadReportStart() const {
@@ -4595,8 +4607,10 @@ bool hwapi::dcDownloadReportFinished() {
     }
 
     if (dcDownloadReportThreadFinished()) {
-        delete m_reportingThread;
-        m_reportingThread = nullptr;
+        if (m_reportingThread) {
+            delete m_reportingThread;
+            m_reportingThread = nullptr;
+        }
     }
 
     return true;