HD404629R Datasheet, PDF (104/157 Pages) Renesas Technology Corp – AS Microcomputer Incorporating a DTMF Generator Circuit

HD404629R 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 92 shows the tone output equivalent circuit. Figure 93 shows the output waveform. One cycle of
this wave consists of 32 slots. Therefore, the output waveform is stable with little distortion. Table 30 lists
the frequency deviation of the MCU from standard DTMF signals.
Table 30 Frequency Deviation of the MCU from Standard DTMF
Standard DTMF (Hz)
MCU (Hz)
Deviation from Standard (%)
R1
697
694.44
–0.37
R2
770
769.23
–0.10
R3
852
851.06
–0.11
R4
941
938.97
–0.22
C1
1,209
1,212.12
0.26
C2
1,336
1,333.33
–0.20
C3
1,477
1,481.48
0.30
C4
1,633
1,639.34
0.39
Note: This frequency deviation value does not include the frequency deviation due to the oscillator
element. Also note that in this case the ratio of the high level and low level widths in the oscillator
waveform due to the oscillator element will be 50%:50%.
VT _ref
GND
Switch control
TONER
TONEC
Figure 92 Tone Output Equivalent Circuit
102