TP3054 has a standard serial PCM interface for connecting to ISDN chips.

I'm still not sure what is your application, since you can not directly connect this CODEC to 8051 because it has no PCM interface.

It would be easy to use an ISAC chip from infineon and then synchronize to B channel with 8 kHz interrupts and capture the compressed voice data from B channel register of ISAC.

Please give me more info about the application, not just about the connection problem, since Voice Compression/Decompression can be done in different ways and maybe more sutable for you than taking this Codec.

Franc