Serial communications circuitry is provided that has bonded first-in-first-out (FIFO) buffer circuitry. The circuitry may include state machine and barrel shifter circuitry that conveys data between the bonded FIFO circuitry and a bonded serial communications path. The bonded FIFO circuitry and the bonded lane may increase the efficiency of the serial communications circuitry by reducing the number of empty data bytes buffered in the FIFO circuitry and conveyed over the serial communications path.