Andi,

To get synchronous 16-bit words from vocoder you can use any 51 derivative with serial peripheral interface (SPI), for instance AT89LS53. For this you have to do the following.

1) Put the device into SLAVE mode. In this mode you can receive bit at any baud rate up to 1 machine cycle (1us at 12MHz clock).

2) Use the channel receive data strobe for synchronization of receiving the new byte (the first half of the 16-bit word).

3) After receiving the first half of the word, keep receiving the next one. 52us is more than enough time to save byte and refresh the receiver buffer pointer to be ready to receive another portion of the frame.

By this way after receiving each byte you will have about 52*8=416us to process the overhead of 12 words or whatever do you wish.

Hope it helps,
George