Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 98)

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98 Rev. 1.3
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 49). 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 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 26, “Cadence Timing,” on page 100).
Table 49. 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