--- a/master/slave_config.c	Mon Mar 16 14:18:55 2015 -0400
+++ b/master/slave_config.c	Thu Mar 26 15:16:21 2015 -0400
@@ -70,6 +70,7 @@
     sc->vendor_id = vendor_id;
     sc->product_code = product_code;
     sc->watchdog_divider = 0; // use default
+    sc->allow_overlapping_pdos = 0; // default not allowed
     sc->watchdog_intervals = 0; // use default
 
     sc->slave = NULL;
@@ -189,10 +190,41 @@
         return -EOVERFLOW;
     }
 
-    fmmu = &sc->fmmu_configs[sc->used_fmmus++];
+    fmmu = &sc->fmmu_configs[sc->used_fmmus];
 
     down(&sc->master->master_sem);
     ec_fmmu_config_init(fmmu, sc, domain, sync_index, dir);
+
+#if 0 //TODO overlapping PDOs
+    // Overlapping PDO Support from 4751747d4e6d
+    // FIXME FIXME FIXME FIXME FIXME FIXME FIXME FIXME FIXME
+    // parent code does not call ec_fmmu_config_domain
+    // FIXME FIXME FIXME FIXME FIXME FIXME FIXME FIXME FIXME
+    fmmu_logical_start_address = domain->tx_size;
+    tx_size = fmmu->data_size;
+
+    // FIXME is it enough to take only the *previous* FMMU into account?
+
+    // FIXME Need to qualify allow_overlapping_pdos with slave->sii.general_flags.enable_not_lrw
+
+    if (sc->allow_overlapping_pdos && sc->used_fmmus > 0) {
+        prev_fmmu = &sc->fmmu_configs[sc->used_fmmus - 1];
+        if (fmmu->dir != prev_fmmu->dir && prev_fmmu->tx_size != 0) {
+            // prev fmmu has opposite direction
+            // and is not already paired with prev-prev fmmu
+            old_prev_tx_size = prev_fmmu->tx_size;
+            prev_fmmu->tx_size = max(fmmu->data_size, prev_fmmu->data_size);
+            domain->tx_size += prev_fmmu->tx_size - old_prev_tx_size;
+            tx_size = 0;
+            fmmu_logical_start_address = prev_fmmu->logical_start_address;
+        }
+    }
+
+    ec_fmmu_config_domain(fmmu, domain, fmmu_logical_start_address, tx_size);
+    // Overlapping PDO Support from 4751747d4e6d
+#endif
+
+    sc->used_fmmus++;
     up(&sc->master->master_sem);
 
     return fmmu->logical_start_address;
@@ -560,6 +592,17 @@
 
 /*****************************************************************************/
 
+void ecrt_slave_config_overlapping_pdos(ec_slave_config_t *sc,
+        uint8_t allow_overlapping_pdos )
+{
+    EC_CONFIG_DBG(sc, 1, "%s(sc = 0x%p, allow_overlapping_pdos = %u)\n",
+                __func__, sc, allow_overlapping_pdos);
+
+    sc->allow_overlapping_pdos = allow_overlapping_pdos;
+}
+
+/*****************************************************************************/
+
 int ecrt_slave_config_pdo_assign_add(ec_slave_config_t *sc,
         uint8_t sync_index, uint16_t pdo_index)
 {