Table 2: Digits vs. input data vs. tone output frequency (parallel mode)

Digit

D3

D2

D1

D0

Tone Output Frequency (Hz)

10

0

0

1

697

+1209

20

0

1

0

697

+1336

30

0

1

1

697

+1477

40

1

0

0

770

+1209

50

1

0

1

770

+1336

60

1

1

0

770

+1477

70

1

1

1

852

+1209

81

0

0

0

852

+1336

When the system is operating in the serial mode

a pull-high resistor is attached to D0~D3 (for

parallel mode) on the input terminal.

For the HT9200B, the S/P pin has to be connected

low for serial mode operation.

Parallel mode ( HT9200B)

The HT9200B provides four data inputs D0~D3

to generate their corresponding DTMF signals.

The S/P has to be connected high to select the

parallel operation mode. Then the input data

codes should be determined. Finally, the CE is

connected low to transmit the DTMF signal

from the DTMF pin.

The TDE time (about 6ms) will be delayed from the

CE falling edge to the DTMF signal output.

The relationship between the digital codes and

the tone output frequency is illustrated in Table 2.

As for the control timing diagram, see Figure 2.

When the system is operating in the parallel

mode, D0~D3 are all in the floating state. Thus,

these data input pins should not float.

Figure 1

HT9200A/B