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Dual Tone Multi Frequency (Dtmf) Generator - Hitachi H8/300L Series Manual

Single-chip microcomputer
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Peripheral Functions

9. Dual Tone Multi Frequency (DTMF) Generator

The H8/3877 Series on-chip dual tone multi frequency (DTMF) generator allows applications
to output DTMF signals.
Features: DTMF signals are used to access telephone exchange equipment and consist of
two sine waves expressed as a frequency matrix. The DTMF generator generates
frequency combinations corresponding to the numbers and symbols on a
telephone touch-pad.
• The DTMF frequencies are generated by dividing the oscillator clock (1.2 to
10 MHz in 400 kHz steps).
• Sine waves are output by a high-precision resistor ladder D/A converter,
allowing low distortion high stability waveforms to be acquired.
• Output of either row group/column group composite signals or independent
signals.
1
2
3
A
4
5
6
B
8
9
C
7
0
#
*
D
112
R1 (697 Hz)
R2 (770 Hz)
R3 (852 Hz)
R4 (941 Hz)

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