Silicon Laboratories SI2494/39 U0-U16 Dial Tone Registers, Register Name Description Default

Models: SI2493/57/34/15/04 SI2494/39

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AN93

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 = 0xC000. 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 48. U0–U16 (Dial Tone Registers)

Register

Name

Description

Default

 

 

 

 

U00

DT1A0

 

0x0800

 

 

 

 

U01

DT1B1

 

0x0000

 

 

 

 

U02

DT1B2

Dial-tone detection filters stage 1 biquad coefficients.

0x0000

 

 

 

 

U03

DT1A2

 

0x0000

 

 

 

 

U04

DT1A1

 

0x0000

 

 

 

 

U05

DT2A0

 

0x00A0

 

 

 

 

U06

DT2B1

 

0x6EF1

 

 

 

 

U07

DT2B2

Dial-tone detection filters stage 2 biquad coefficients.

0xC4F4

 

 

 

 

U08

DT2A2

 

0xC000

 

 

 

 

U09

DT2A1

 

0x0000

 

 

 

 

U0A

DT3A0

 

0x00A0

 

 

 

 

U0B

DT3B1

 

0x78B0

 

 

 

 

U0C

DT3B2

Dial-tone detection filters stage 3 biquad coefficients.

0xC305

 

 

 

 

U0D

DT3A2

 

0x4000

 

 

 

 

U0E

DT3A1

 

0xB50A

 

 

 

 

U0F

DT4A0

 

0x0400

 

 

 

 

U10

DT4B1

 

0x70D2

 

 

 

 

U11

DT4B2

Dial-tone detection filters stage 4 biquad coefficients.

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

 

 

 

 

Rev. 1.3

97

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Silicon Laboratories SI2494/39 manual U0-U16 Dial Tone Registers, 2. U00-U16 Dial Tone Detect Filter Registers