PCD3755AT datasheet(10/32 Pages) PHILIPS

10 / 32 page

1997 Apr 16

Philips Semiconductors

Product speciﬁcation

8-bit microcontrollers with DTMF generator,

8 kbytes OTP and 128 bytes EEPROM

PCD3755A; PCD3755E;

PCD3755F

6.4

DTMF frequencies

Assuming an oscillator frequency fxtal = 3.58 MHz, the

DTMF standard frequencies can be implemented as

shown in Table 6.

The relationships between telephone keyboard symbols,

DTMF frequency pairs and the frequency register contents

are given in Table 7.

Table 6

DTMF standard frequencies and their

implementation; value = LGF, HGF contents

Table 7

Dialling symbols, corresponding DTMF

frequency pairs and frequency register contents

VALUE

(HEX)

FREQUENCY (Hz)

DEVIATION

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

1209

1206.45

−0.21 −2.55

1336

1341.66

0.42

5.66

1477

1482.21

0.35

5.21

1633

1638.24

0.32

5.24

TELEPHONE

KEYBOARD

SYMBOLS

DTMF FREQ.

PAIRS

(Hz)

LGF

VALUE

(HEX)

HGF

VALUE

(HEX)

(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)

6.5

Modem frequencies

Again assuming an oscillator frequency fxtal = 3.58 MHz,

the standard modem frequencies can be implemented as

in Table 8. It is suggested to define the frequency by the

HGF register while the LGF register contains 00H,

disabling Low Group Frequency generation.

Table 8

Standard modem frequencies and their

implementation

Notes

1. Standard is V.21.

2. Standard is Bell 103.

3. Standard is Bell 202.

4. Standard is V.23.

HGF

VALUE

(HEX)

FREQUENCY (Hz)

DEVIATION

MODEM

GENERATED

(%)

(Hz)

980(1)

978.82

−0.12 −1.18

1180(1)

1179.03

−0.08 −0.97

1070(2)

1073.33

0.31

3.33

1270(2)

1265.30

−0.37 −4.70

1200(3)

1197.17

−0.24 −2.83

2200(3)

2192.01

−0.36 −7.99

1300(4)

1296.94

−0.24 −3.06

2100(4)

2103.14

0.15

3.14

1650(1)

1655.66

0.34

5.66

1850(1)

1852.77

0.15

2.77

2025(2)

2021.20

−0.19 −3.80

2225(2)

2223.32

−0.08 −1.68

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