My comment about not needing sync was based upon the serial port being ready to read before the DSP starts sending, and handshaking being used so that no data gets dropped nor buffers get overrun. I think this is entirely possible. I've done this sort of thing before and always received an even number of bytes. If I didn't, I would declare an error.
The only time sync would be necessary is if you would start reading in the middle of a stream and/or the DSP would send faster than the port could read along with no handshaking involved. I would not want to design a system this way. If you start reading in the middle of a stream, you would be missing some data anyway. Seems like nobody wants to use handshaking these days. All I see is three wire RS232 (Tx, Rx, Gnd). RTS and CTS are there, so is XON and XOFF. Use it and you won't lose data and you won't need to sync anything.
