HD404639R Datasheet, PDF (105/135 Pages) Renesas Technology Corp – 4-Bit Single-Chip Microcomputer

HD404639R Series
DTMF Output: The sine waves of the row-group and column-group are individually converted in the D/A
conversion circuit which provides a high-precision ladder resistance. The DTMF output pins (TONER,
TONEC) transmit the sine waves of the row-group and column-group, respectively. Figure 87 shows the
tone output equivalent circuit. Figure 88 shows the output waveform. One cycle of this wave consists of 32
slots. Therefore, the output waveform is stable with little distortion. Table 28 lists the frequency deviation
of the MCU from standard DTMF signals.
VT_ref
GND
Switch control
VT_ref
TONER
TONEC
Figure 87 Tone Output Equivalent Circuit
1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20 2122 23 24 25 26 27 28 29 30 31 32
GND
Time slots
Figure 88 Waveform of Tone Output
103