M38264EBFS datasheet(41/91 Pages) RENESAS

41 / 91 page

Rev.1.00

Sep 06, 2006

page 41 of 88

REJ03B0181-0100

3826 Group (One Time PROM version)

DTMF Function (Dual Tone Multi Frequency)

DTMF function is used to output the result which generated auto-

matically the waveform of sine wave of two kinds of different

frequency, and added two kinds of this sine wave as an analog

value.

DTMF output waveform can be output from DA1 pin. DTMF wave-

form is output by setting “1” (enabled) to the DTMF/DA1 output

enable bit (bit 0 of address 003616), and setting “1” to the DTMF/

DA1 selection bit (bit 2 of address 003616). At this time, set “0” (in-

put state) to the direction register of ports P56/DA1 pin and pull-up

resistor to be OFF state.

In order to set two kinds of frequency which generates DTMF

waveform, write a value in the DTMF high group timer and the

DTMF low group timer, respectively. The value written in each

above-mentioned timer is n, the sine wave of the following fre-

quency can be generated.

f =

(Hz)

Set “0616” or more to the DTMF high group timer and the DTMF

low group timer. After reset release, “0616” is automatically set to

them.

f(XIN)/2

(n+1) ✕ 32

The digital value for one period of high group and low group out-

put is shown in Figure 43.

DTMF output is automatically input to high-order 6 bits of the D/A1

conversion register as 6-bit D/A data. The low-order 2 bits of the

D/A1 conversion register are fixed to the value written in the D/A1

conversion register.

Moreover, only the sine wave of high group can be output by set-

ting “1” to the bit 4 of the D/A control register. By setting “1” to the

bit 5 of the D/A control register similarly, only the sine wave of low

group can be output. Writing to the DTMF high group timer and

the DTMF low group timer can also be changed to “writing to latch

and timer simultaneously” by setting “1” to the bit 6 of the D/A con

trol register. “Writing to only latch” is set after reset release. If the

D/A1 conversion register is read when the DTMF function is

selected,the digital value of DTMF output can be read.

Fig. 43 Waveform data of high group and low group

1416

2816

3C16

5016

6416

7816

016

1416

2816

3C16

5016

6416

7816

016

DA data of low group waveform (1 period) for DTMF

DA data of high group waveform (1 period) for DTMF

* This is the value set to DA1 conversion register when the low-order 2 bits are “0”.

Conversion time of high group ROM

Conversion time of low group ROM

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