The present invention provides a
synchronizing data protocol comprising one or more serial input-output (SIO) control word(s) and data passed across a
high voltage interface, to allow the
elimination of a
frame synchronization signal (and corresponding AC
coupling capacitors). The present invention has particular applicability to, e.g., time division multiplexed (TDM) data, serial data communication devices, or
synchronous serial communication interfaces in general, and to the communication between a controller and a codec in an audio codec device in accordance with the AC '97 Specification, i.e., the AC Link. The
synchronizing data protocol is implemented over a transmit
data signal line to provide occasional synchronization (i.e., not frame-by-
frame synchronization) between the two communicating devices. The master device includes a
preamble insertion module to insert a predetermined
preamble code word into the transmitted
data stream. An interrupt is sent to the slave device by withholding the data
clock signal for a predetermined amount of time. Upon
receipt of the interrupt, the slave device monitors the
data stream for the presence of the
preamble code word. Upon detection of the preamble
code word, data transmitted by the codec is again enabled.