PCD3359AP datasheet(9/32 Pages) PHILIPS

9 / 32 page

1998 May 11

Philips Semiconductors

Product speciﬁcation

8-bit microcontroller with DTMF

generator and 128 bytes EEPROM

PCD3359A

6.2

Melody output (P1.7/MDY)

The melody output (P1.7/MDY) is very useful for

generating musical notes when a purely sinusoidal signal

is not required, such as for ringer applications.

If bit EMO = 1 in the Melody and Port Interrupt Control

square wave with the frequency defined by the HGF

contents is output on line P1.7/MDY. The square wave

(duty cycle = 12

⁄23 or 52%) will include the attenuated

harmonics of the base frequency, which is defined by the

contents of the HGF register (Table 3). However, even

higher frequency notes may be produced since the

low-pass filtering on the TONE output is not applied to the

P1.7/MDY output. This results in the minimum decimal

value x in the HGF register (see equation in Section 6.3)

being 2 for the P1.7/MDY output, rather than 60 for the

TONE output. A sinusoidal TONE output is produced at the

same time as the melody square wave, but due to the

filtering, the higher frequency sine waves with x < 60 will

not appear at the TONE output.

Since the melody output is shared with P1.7, the port

flip-flop of P1.7 has to be set HIGH before using the

melody output. This is to avoid conflicts between melody

and port outputs. The melody output drive depends on the

configuration of port P1.7/MDY; see Chapter 14, Table 25.

6.3

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 of the sine wave generated ‘f’ is dependent

on the crystal frequency ‘fxtal’ and the decimal value ‘x’ held

in the frequency registers (HGF and LGF). The variables

are related by the equation:

; 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.

xtal

23 x

()

[]

---------------------------------

PCD3359AP Datasheet(PDF) 9 Page - NXP Semiconductors

PCD3359AP Datasheet(HTML) 9 Page - NXP Semiconductors

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Datasheet Descarga

Enlace URL