A N 9 3
104
Rev. 1.4
5.7.2. U00–U16 (Dial Tone Detect Filter Registers)
U00–U13 set the biquad filter coefficients for stages 1–4 of the dial-tone detection filter. U14, U15, and U16 set the
dial-tone detection output scaler, on threshold and off threshold, respectively.
The thresholds are empirically found scalars and have no units. These coefficients are programmed as 16-bit,
two’s complement values. All A0 values are in 3.12 format where 1.0 = 0x1000. All other coefficients are in 1.14
format where 1.0 = 0x4000. Default settings meet FCC requirements. Additionally, register U34 sets the time
window in which a dial tone can be detected. Register U35 sets the minimum time within the U34 window that the
dial tone must be present for a valid detection. See "5.7.5. U34–U35 (Dial Tone Timing Register)" for more
information.
Table 59. U0–U16 (Dial Tone Registers)
Register
Name
Description
Default
U00
DT1A0
Dial-tone detection filters stage 1 biquad coefficients.
0x0800
U01
DT1B1
0x0000
U02
DT1B2
0x0000
U03
DT1A2
0x0000
U04
DT1A1
0x0000
U05
DT2A0
Dial-tone detection filters stage 2 biquad coefficients.
0x00A0
U06
DT2B1
0x6EF1
U07
DT2B2
0xC4F4
U08
DT2A2
0xC000
U09
DT2A1
0x0000
U0A
DT3A0
Dial-tone detection filters stage 3 biquad coefficients.
0x00A0
U0B
DT3B1
0x78B0
U0C
DT3B2
0xC305
U0D
DT3A2
0x4000
U0E
DT3A1
0xB50A
U0F
DT4A0
Dial-tone detection filters stage 4 biquad coefficients.
0x0400
U10
DT4B1
0x70D2
U11
DT4B2
0xC830
U12
DT4A2
0x4000
U13
DT4A1
0x80E2
U14
DTK
Dial-tone detection filter output scaler.
0x0009
U15
DTON
Dial-tone detection ON threshold.
0x00A0
U16
DTOF
Dial-tone detection OFF threshold.
0x0070
Содержание Si2404
Страница 2: ...AN93 2 Rev 1 4 ...
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Страница 290: ...AN93 290 Rev 1 4 Figure 57 256 Band Spectral Display Figure 58 2048 Band Spectral Display ...
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