MB86437 Datasheet, PDF (11/35 Pages) Fujitsu Component Limited. – 3 V Single Power Supply Audio Interface Unit (AIU)

MB86437
(5) Tone generation circuit
This section describes the frequency settings and output control.
• Tone frequency control register
The clock used to generate tones is the clock input from TCLK divided by 1 or 2. The divide ratio is set by the data
at address 01110. Also, 12 division and 24 division modes are available to generate a smooth frequency even at
low frequencies.
Table 2 Register Control for the TONE Clock Frequency
Address 01110
D4
D3
0
0
0
1
1
0
1
1
Tone Generation Clock (fIN)
Frequency input to TCLK
Frequency input to TCLK
Frequency input to TCLK divided by 2
Prohibited
Waveform Division
12 divisions
24 divisions
24 divisions
The following formula specifies the frequencies that can be set by the tone frequency control register.
Set frequency f = fIN/(M × (1 + n)), M = division mode (12 or 24)
n = 4, 5, ..., 255 (fIN: Tone generation clock)
fIN = 4 MHz max.
Therefore, the range of available frequencies in 12 division mode and fIN = 512 kHz, and in 24 division mode and
fIN = 1024 kHz is:
fmin = 167 Hz, fmax = 8533 Hz
Table 3 lists the frequency settings for all the standard DTMF frequencies.
Table 3 Tone Frequency Register Control
(Setting: 12 divisions and fIN = 512 kHz, or 24 divisions and fIN = 1024 kHz)
Standard
Address
Address
Tone Type
Frequency
(Example of
generated
Set
Frequency
01010/01100
Data
01011/01101
n
Data
frequency)
D4 D3 D2 D1 D0 D4 D3 D2 D1 D0
Service tones
(Single tone)
400 Hz
2000 Hz
398.7 Hz — 0 1 1 0 ∗ 1 0 1 0 106
2031.7 Hz — 0 0 0 1 ∗ 0 1 0 0 20
697 Hz
699.4 Hz — 0 0 1 1 ∗ 1 1 0 0 60
Low tones
D
T
770 Hz
852 Hz
941 Hz
775.7 Hz — 0 0 1 1 ∗ 0 1 1 0 54
853.3 Hz — 0 0 1 1 ∗ 0 0 0 1 49
948.1 Hz — 0 0 1 0 ∗ 1 1 0 0 44
M
1209 Hz 1219.0 Hz — 0 0 1 0 ∗ 0 0 1 0 34
F
1336 Hz 1333.3 Hz — 0 0 0 1 ∗ 1 1 1 1 31
High tones
1477 Hz 1471.3 Hz — 0 0 0 1 ∗ 1 1 0 0 28
1633 Hz 1641.0 Hz — 0 0 0 1 ∗ 1 0 0 1 25
Error
–0.32%
1.56%
0.34%
0.74%
0.15%
0.75%
0.82%
–0.20%
–0.38%
0.48%
Notes: • Settings are shown in binary notation.
• Error is the error between the set frequency and standard frequency.
• Set n to 4 or higher and set a frequency of 5 kHz or less.
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