diff --git a/TODO b/TODO
index ae4eec10..448b1bb4 100644
--- a/TODO
+++ b/TODO
@@ -13,8 +13,7 @@ Version 1.5.0:
 * Distributed clocks:
     - Delay calculation.
     - Synchronize the reference clock to the master clock.
-    - Reference clock zero.
-    - Configuration must exist, config state machine.
+	- Output reference clock and application time in 'ethercat master'.
 * Read alias from register 0x0012 instead of SII.
 * Finish library implementation.
 * Re-work EoE code.
diff --git a/master/fsm_master.c b/master/fsm_master.c
index b1de6f9a..66f22ca7 100644
--- a/master/fsm_master.c
+++ b/master/fsm_master.c
@@ -828,6 +828,9 @@ void ec_fsm_master_state_scan_slave(
     master->scan_busy = 0;
     wake_up_interruptible(&master->scan_queue);
 
+	// find DC reference clock
+	ec_master_find_dc_ref_clock(master);
+	
     // Attach slave configurations
     ec_master_attach_slave_configs(master);
 
diff --git a/master/master.c b/master/master.c
index 99efbdf3..7a641d4f 100644
--- a/master/master.c
+++ b/master/master.c
@@ -128,6 +128,8 @@ int ec_master_init(ec_master_t *master, /**< EtherCAT master */
     
     INIT_LIST_HEAD(&master->configs);
 
+	master->app_time = 0ULL;
+
     master->scan_busy = 0;
     master->allow_scan = 1;
     init_MUTEX(&master->scan_sem);
@@ -212,12 +214,13 @@ int ec_master_init(ec_master_t *master, /**< EtherCAT master */
     // init sync datagram
     ec_datagram_init(&master->sync_datagram);
     snprintf(master->sync_datagram.name, EC_DATAGRAM_NAME_SIZE, "sync");
-    ret = ec_datagram_armw(&master->sync_datagram, 0 /* FIXME */, 0x0910, 4);
+    ret = ec_datagram_prealloc(&master->sync_datagram, 4);
     if (ret < 0) {
         ec_datagram_clear(&master->sync_datagram);
         EC_ERR("Failed to allocate synchronisation datagram.\n");
         goto out_clear_ref_sync;
     }
+	ec_master_find_dc_ref_clock(master);
 
     // init character device
     ret = ec_cdev_init(&master->cdev, master, device_number);
@@ -1344,6 +1347,30 @@ int ec_master_debug_level(
     return 0;
 }
 
+/*****************************************************************************/
+
+/** Finds the DC reference clock.
+ */
+void ec_master_find_dc_ref_clock(
+        ec_master_t *master /**< EtherCAT master. */
+		)
+{
+	ec_slave_t *slave;
+	uint16_t ref_clock_addr = 0xffff;
+
+    for (slave = master->slaves;
+            slave < master->slaves + master->slave_count;
+            slave++) {
+		if (slave->base_dc_supported) {
+			ref_clock_addr = slave->station_address;
+			break;
+		}
+    }
+
+	// This call always succeeds, because the datagram has been pre-allocated.
+	ec_datagram_frmw(&master->sync_datagram, ref_clock_addr, 0x0910, 4);
+}
+
 /******************************************************************************
  *  Application interface
  *****************************************************************************/
diff --git a/master/master.h b/master/master.h
index 3bd91edc..b7659f08 100644
--- a/master/master.h
+++ b/master/master.h
@@ -233,6 +233,8 @@ ec_domain_t *ecrt_master_create_domain_err(ec_master_t *);
 ec_slave_config_t *ecrt_master_slave_config_err(ec_master_t *, uint16_t,
         uint16_t, uint32_t, uint32_t);
 
+void ec_master_find_dc_ref_clock(ec_master_t *);
+
 /*****************************************************************************/
 
 #endif