Silicon Laboratories SI2493/57/34/15/04, SI2494/39 manual BPF Biquad Values, 400/440

AN93

Table 50. BPF Biquad Values (Continued)

BPF Biquad	Stage 1	Stage 2		Stage 3	Stage 4	Output Scalar
Values
K	—	—		—	—	0x0005
			400/440
A0	0x0020	0x0200		0x0400	0x0040	—
B1	0x7448	0x7802		0x73D5	0x75A7	—
B2	0xC0F6	0xC0CB		0xC2A4	0xC26B	—
A2	0x4000	0x4000		0x4000	0x4000	—
A1	0x96AB	0x8359		0x8D93	0x85C1	—
K	—	—		—	—	0x0008

Example: The United States specifies a busy tone “on” time from 450 to 550 ms and “off” time from 450 to 550 ms. Thus the minimum “on” and “off” times are 0.45 s each , and the maximum “on” and “off” times are 0.55 s each.

The busy cadence minimum on time is 0.45 s, thus BMOT = 0.45 x 7200 = 0x0CA8.

The busy cadence minimum total time is 0.45 s + 0.45 s = 0.9 s, thus BMTT = 0.9 x 7200 = 6480 = 0x1950.

The maximum total time is 0.55 s + 0.55 s = 1.1 s, thus BDLT = (1.1 – 0.9) x 7200 = 1440 = 0x05A0.

The hexadecimal values are stored in the appropriate registers using the AT:Uhh command. Detection parameters can be wider than the minimum specifications. This is often done in the modem defaults and other suggested settings so that one set of parameters can cover a broad number of different country requirements.

Maximum Cadence

TOTAL Time

Minimum ON Time	Minimum Cadence		Cadence		Delta
(BMOT)		TOTAL Time		Time (BDLT)
(RMOT)		(BMTT)		(RDLT)
		(RMTT)

Figure 26. Cadence Timing

100 Rev. 1.3