diff --git a/src/emu/machine/z80dart.c b/src/emu/machine/z80dart.c
index 8791de96b04..e23b39a65d8 100644
--- a/src/emu/machine/z80dart.c
+++ b/src/emu/machine/z80dart.c
@@ -162,11 +162,11 @@ const int WR5_RTS					= 0x02;
 const int WR5_CRC16					= 0x04; // not supported
 const int WR5_TX_ENABLE				= 0x08;
 const int WR5_SEND_BREAK			= 0x10;
-const int WR5_TX_WORD_LENGTH_MASK	= 0xc0;
+const int WR5_TX_WORD_LENGTH_MASK	= 0x60;
 const int WR5_TX_WORD_LENGTH_5		= 0x00;
-const int WR5_TX_WORD_LENGTH_7		= 0x40;
-const int WR5_TX_WORD_LENGTH_6		= 0x80;
-const int WR5_TX_WORD_LENGTH_8		= 0xc0;
+const int WR5_TX_WORD_LENGTH_6		= 0x40;
+const int WR5_TX_WORD_LENGTH_7		= 0x20;
+const int WR5_TX_WORD_LENGTH_8		= 0x60;
 const int WR5_DTR					= 0x80;