Silicon Laboratories SI2493/57/34/15/04, SI2494/39 manual U17-U30 Busy Tone Detect Registers

AN93

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		0x0800
U18	BT1B1		0x0000
		Busy-tone detection filter stage 1 biquad coefficients.
U19	BT1B2		0x0000
U1A	BT1A2		0x0000
U1B	BT1A1		0x0000
U1C	BT2A0		0x00A0
U1D	BT2B1		0x6EF1
		Busy-tone detection filter stage 2 biquad coefficients.
U1E	BT2B2		0xC4F4
U1F	BT2A2		0xC000
U20	BT2A1		0x0000
U21	BT3A0		0x00A0
U22	BT3B1		0x78B0
		Busy-tone detection filter stage 3 biquad coefficients.
U23	BT3B2		0xC305
U24	BT3A2		0x4000
U25	BT3A1		0xB50A
U26	BT4A0		0x0400
U27	BT4B1		0x70D2
		Busy-tone detection filter stage 4 biquad coefficients.
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

98 Rev. 1.3