V.FC
V.FC
(communications, protocol)V.34 modems will also support V.FC if the manufacturercurrently supports V.FC.
The first V.FC modems were shipped in November 1993 and therehave been many thousands sold. There will probably be inexcess of a million V.FC modems installed by the end of 1994.
V.FC was intended to take some of the techniques beingproposed for V.34 and put them into a real modem that peoplecould use. This also gave a lot of people the opportunity totry out 28.8 kilobit per second operation for the first time.There was never any intention from Hayes or Rockwell (whoworked together for two years on V.FC) that V.FC would becompatible with V.34 - even if they had wanted it, otherswould have made sure it didn't happen! In fact, they made thestart-up deliberately different from V.34 so that it would beeasy to distinguish between the two and easier to makedual-mode V.FC/V.34 modems.
V.FC is quite different from V.34. Most of thesignal-processing algorithms, whilst based on the sametheory, are implemented in different ways. V.34 has someextra things like a secondary channel and a special mode for28.8 kilobit per second fax.
The Rockwell V.FC implementation uses a single-chipmask-programmed DSP for all the signal processing functions.You can also buy a modem controller chip from Rockwell to gowith it which implements AT commands, error-control andcompression. Hayes made their own controller using theMotorola 68302 processor. When it comes to an upgradefrom V.FC to V.34 you have to have a new, masked DSP chip andnew controller firmware to implement all the V.34-specificfeatures. This means that Rockwell-DSP based modems must bereturned to the manufacturer for upgrade. Upgraded modemswill talk to either V.FC or V.34 modems.