National Semiconductor NS TP5088 Tone Dialer chip providessimple means DTMF generation and simple interfacing with uProcessor. Aboveis a truth table for DTMF generation TABLE. The Tone Output frequency isfor TP5088 generation, not a standard, but it works with all most DTMFdecoder chip, say MT8870. Please note that the CODE for KEYBOARD equivalentfor number 0 is 10D or 1010B.
A typical application circuitinterfacing with microprocessors for direct generation of DTFM signal connectedto phone line through 600:600 Ohm transformer. The output tone level canbe adjusted by changing Re value..
