diff --git a/src/emu/machine/mos6551.c b/src/emu/machine/mos6551.c
index 3818f19071e..e50cf53c420 100644
--- a/src/emu/machine/mos6551.c
+++ b/src/emu/machine/mos6551.c
@@ -202,6 +202,18 @@ void mos6551_device::update_serial()
 {
 	int brg = m_ctrl & CTRL_BRG_MASK;
 
+	int num_data_bits = 8;
+	int stop_bit_count = 1;
+	int parity_code = PARITY_NONE;
+
+	switch (m_ctrl & CTRL_WL_MASK)
+	{
+	case CTRL_WL_8: num_data_bits = 8; break;
+	case CTRL_WL_7: num_data_bits = 7; break;
+	case CTRL_WL_6: num_data_bits = 6; break;
+	case CTRL_WL_5: num_data_bits = 5; break;
+	}
+
 	set_data_frame(num_data_bits, stop_bit_count, parity_code, false);
 
 	if (brg == CTRL_BRG_16X_EXTCLK)
@@ -223,18 +235,6 @@ void mos6551_device::update_serial()
 		{
 			set_rcv_rate(m_ext_rxc / 16);
 		}
-
-		int num_data_bits = 8;
-		int stop_bit_count = 1;
-		int parity_code = PARITY_NONE;
-
-		switch (m_ctrl & CTRL_WL_MASK)
-		{
-		case CTRL_WL_8: num_data_bits = 8; break;
-		case CTRL_WL_7: num_data_bits = 7; break;
-		case CTRL_WL_6: num_data_bits = 6; break;
-		case CTRL_WL_5: num_data_bits = 5; break;
-		}
 	}
 
 	if (m_cmd & CMD_DTR)
diff --git a/src/emu/machine/z80dart.c b/src/emu/machine/z80dart.c
index fe36bb6152a..4dcd79289e3 100644
--- a/src/emu/machine/z80dart.c
+++ b/src/emu/machine/z80dart.c
@@ -1303,20 +1303,6 @@ WRITE_LINE_MEMBER( z80dart_channel::txc_w )
 
 void z80dart_channel::update_serial()
 {
-	int clocks = get_clock_mode();
-
-	set_data_frame(num_data_bits, stop_bit_count, parity_code, false);
-
-	if (m_rxc > 0)
-	{
-		set_rcv_rate(m_rxc / clocks);
-	}
-
-	if (m_txc > 0)
-	{
-		set_tra_rate(m_txc / clocks);
-	}
-
 	int num_data_bits = get_rx_word_length();
 	int stop_bit_count = get_stop_bits();
 	int parity_code = PARITY_NONE;
@@ -1328,6 +1314,20 @@ void z80dart_channel::update_serial()
 		else
 			parity_code = PARITY_ODD;
 	}
+
+	set_data_frame(num_data_bits, stop_bit_count, parity_code, false);
+
+	int clocks = get_clock_mode();
+
+	if (m_rxc > 0)
+	{
+		set_rcv_rate(m_rxc / clocks);
+	}
+
+	if (m_txc > 0)
+	{
+		set_tra_rate(m_txc / clocks);
+	}
 }