AN93
Rev. 1.4
105
5.7.3. U17–U30 (Busy Tone Detect Filter Registers)
U17–U2A set the biquad filter coefficients for stages 1–4 of the busy-tone detection filter, and U2B, U2C, and U2D
set the busy-tone detection output scalar on threshold and off threshold, respectively (see Table 60). 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 values meet FCC requirements.
U2E, U2F, and U30 set the busy cadence minimum total time (BMTT), busy cadence delta time (BDLT), and busy
cadence minimum on time (BMOT), respectively. Settings for busy cadences are specified as a range for ON time
(minimum ON and maximum ON) and a range for OFF time (minimum OFF and maximum OFF). The three values
represented by BMTT, BDLT, and BMOT fully specify these ranges. BMTT (minimum total time) is equal to the
minimum ON time plus the minimum OFF time. BDLT (allowable delta) is equal to the maximum total time
(maximum ON time plus the maximum OFF time) minus the minimum total time (BMTT). BMOT is the minimum
ON time. The values stored in the registers are the hexadecimal representation of the times in seconds multiplied
by 7200. Default values meet FCC requirements (see Figure 27, “Cadence Timing,” on page 107).
Table 60. U17–U30 (Busy Tone Detect Registers)
Register
Name
Description
Default
U17
BT1A0
Busy-tone detection filter stage 1 biquad coefficients.
0x0800
U18
BT1B1
0x0000
U19
BT1B2
0x0000
U1A
BT1A2
0x0000
U1B
BT1A1
0x0000
U1C
BT2A0
Busy-tone detection filter stage 2 biquad coefficients.
0x00A0
U1D
BT2B1
0x6EF1
U1E
BT2B2
0xC4F4
U1F
BT2A2
0xC000
U20
BT2A1
0x0000
U21
BT3A0
Busy-tone detection filter stage 3 biquad coefficients.
0x00A0
U22
BT3B1
0x78B0
U23
BT3B2
0xC305
U24
BT3A2
0x4000
U25
BT3A1
0xB50A
U26
BT4A0
Busy-tone detection filter stage 4 biquad coefficients.
0x0400
U27
BT4B1
0x70D2
U28
BT4B2
0xC830
U29
BT4A2
0x4000
U2A
BT4A1
0x80E2
U2B
BTK
Busy-tone detection filter output scaler.
0x0009
U2C
BTON
Busy-tone detection ON threshold.
0x00A0
U2D
BTOF
Busy-tone detection OFF threshold.
0x0070
U2E
BMTT
Busy cadence minimum total time in seconds multiplied by 7200.
0x0870
U2F
BDLT
Busy cadence delta time in seconds multiplied by 7200.
0x25F8
U30
BMOT
Busy cadence minimum on time in seconds multiplied by 7200.
0x0438
Summary of Contents for Si2404
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