I use these in the GameServer driver. Seem to work for me just fine even at 115.2k baud. ACIA_Data = $c0a8 ACIA_Status = $c0a9 sendByte ;Sends byte to SSC (data is in X) .sendLoop LDA ACIA_Status AND #$10 BEQ .sendLoop STX ACIA_Data RTS readByte ;Poll for next byte (returns in A) LDA ACIA_Status AND #$08 BEQ readByte LDA ACIA_Data RTS