PCD3353CH データシートの表示（PDF） - Philips Electronics
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PCD3353CH Datasheet PDF : 36 Pages
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Philips Semiconductors
8-bit microcontrollers with DTMF generator
and 128 bytes EEPROM
Product specification
PCA3351C; 52C; 53C;
PCD3351A; 52A; 53A
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.
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 4).
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 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 26.
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 from either HGF
or LGF is a function of the decimal value ‘x’ held in the
register. The variables are related by the equation:
f = [---2---3----(-f--xx--t-a-+--l---2----)--] ; where 60 ≤ x ≤ 255 for TONE output.
6.4 DTMF frequencies
Assuming an oscillator frequency fxtal = 3.58 MHz, the
DTMF standard frequencies can be implemented as
shown in Table 7.
The relationships between telephone keyboard symbols,
DTMF frequency pairs and the frequency register contents
are given in Table 8.
Table 7 DTMF standard frequencies and their
implementation; value = LGF, HGF contents
VALUE
FREQUENCY (Hz)
DEVIATION
(HEX) STANDARD GENERATED (%) (Hz)
DD
697
697.90
0.13 0.90
C8
770
770.46
0.06 0.46
B5
852
850.45
−0.18 −1.55
A3
941
943.23
0.24 2.23
7F
1209
1 206.45
−0.21 −2.55
72
1336
1 341.66
0.42 5.66
67
1477
1 482.21
0.35 5.21
5D
1633
1 638.24
0.32 5.24
Table 8 Dialling symbols, corresponding DTMF
frequency pairs and frequency register contents
TELEPHONE DTMF FREQ.
KEYBOARD PAIRS
SYMBOLS
(Hz)
0
(941, 1336)
1
(697, 1209)
2
(697, 1336)
3
(697, 1477)
4
(770, 1209)
5
(770, 1336)
6
(770, 1477)
7
(852, 1209)
8
(852, 1336)
9
(852, 1477)
A
(697, 1633)
B
(770, 1633)
C
(852, 1633)
D
(941, 1633)
•
(941, 1209)
#
(941, 1477)
LGF
VALUE
(HEX)
A3
DD
DD
DD
C8
C8
C8
B5
B5
B5
DD
C8
B5
A3
A3
A3
HGF
VALUE
(HEX)
72
7F
72
67
7F
72
67
7F
72
67
5D
5D
5D
5D
7F
67
1999 Oct 28
10
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