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PCD3350A データシートの表示（PDF） - Philips Electronics

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PCD3350A

8-bit microcontroller with DTMF generator, 256 bytes EEPROM and real-time clock

Philips Electronics

PCD3350A Datasheet PDF : 36 Pages

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Philips Semiconductors

8-bit microcontroller with DTMF generator,

256 bytes EEPROM and real-time clock

Product speciﬁcation

PCD3350A

If EDCO = 1 and DIV3 = 1 in the MDYCON register: a

square wave with the frequency fDTMF = 1⁄3 × fxtal is output

on the derivative port line DP1.7/DCO. If EDCO = 1 and

DIV3 = 0: a square wave with the frequency fDTMF = fxtal is

output on the derivative port line DP1.7/DCO.

The melody output drive depends on the configuration of

port P1.7/MDY, see Chapter 14, Table 27.

6.4 Frequency registers

The two frequency registers HGF and LGF define two

frequencies. From these, the digital sine synthesizers

together with the Digital-to-Analog Converters (DACs)

construct two sine waves. Their amplitudes are precisely

scaled according to the bandgap voltage reference. This

ensures tone output levels independent of supply voltage

and temperature. The amplitude of the Low Group

Frequency sine wave is attenuated by 2 dB compared to

the amplitude of the High Group Frequency sine wave.

The two sine waves are summed and then filtered by an

on-chip switched capacitor and RC low-pass filters.

These guarantee that all DTMF tones generated fulfil the

CEPT recommendations with respect to amplitude,

frequency deviation, total harmonic distortion and

suppression of unwanted frequency components.

The value 00H in a frequency register stops the

corresponding digital sine synthesizer. If both frequency

registers contain 00H, the whole frequency generator is

shut off, resulting in lower power consumption.

The frequency ‘f’ of the sine wave generated from either of

the frequency registers is a function of the clock frequency

‘fxtal’ and the decimal value ‘x’ held in the register.

The equation relating these variables is:

f = -[---2---3-----(-f--xx--t-a-+--l---2----)---]--; where 60 ≤ x ≤ 255.

The frequency limitation given by x ≥ 60 is due to the

low-pass filters which would attenuate higher frequency

sine waves.

6.5 DTMF frequencies

Assuming an oscillator frequency fxtal = 3.58 MHz, the

DTMF standard frequencies can be implemented as

shown in Table 5.

The relationships between telephone keyboard symbols,

DTMF frequency pairs and the frequency register contents

are given in Table 6.

Table 5 DTMF standard frequencies and their

implementation; value = LGF, HGF contents

VALUE

FREQUENCY (Hz)

DEVIATION

(HEX) STANDARD GENERATED (%) (Hz)

697

697.90

0.13 0.90

770

770.46

0.06 0.46

852

850.45

−0.18 −1.55

941

943.23

0.24 2.23

1 209

1 206.45

−0.21 −2.55

1 336

1 341.66

0.42 5.66

1 477

1 482.21

0.35 5.21

1 633

1 638.24

0.32 5.24

Table 6 Dialling symbols, corresponding DTMF

frequency pairs and frequency register contents

TELEPHONE DTMF FREQ.

KEYBOARD PAIRS

SYMBOLS

(Hz)

(941, 1336)

(697, 1209)

(697, 1336)

(697, 1477)

(770, 1209)

(770, 1336)

(770, 1477)

(852, 1209)

(852, 1336)

(852, 1477)

(697, 1633)

(770, 1633)

(852, 1633)

(941, 1633)

•

(941, 1209)

(941, 1477)

LGF

VALUE

(HEX)

HGF

VALUE

(HEX)

1996 Dec 18

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