Specifications

AN93
78 Rev. 0.9
Example: The United States specifies a busy tone with on time from 450 to 550 ms and off time from 450 to
550 ms. Thus, minimum ON time equals 0.450 s; maximum ON time equals 0.550 s; minimum OFF time equals
0.450 sec, and maximum OFF time equals 0.550 sec. Busy Cadence Minimum Total Time = 0.450 s +
0.450 s = 0.900 s. Therefore, BMTT = (0.900)(7200)d = 0x1950. Maximum total time = 0.550 s +
0.550 s = 1100 ms; so, BDLT = (1.10–0.900)(7200)d = 0x05A0, and BMOT = (0.450)(7200)d = 0x0CA8. The
hexadecimal values are stored in the appropriate registers using the AT:Uhh command where hh is the U-Register
number (hexadecimal address). 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 large number
of different country requirements.
Figure 15. Cadence Timing
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
Table 36. BPF Biquad Values (Continued)
BPF Biquad
Values
Stage 1 Stage 2 Stage 3 Stage 4 Output Scalar
Maximum Cadence
TOTAL Time
Minimum Cadence
TOTAL Time
(BMTT)
(RMTT)
Cadence Delta
Time
(BDLT)
(RDLT)
Minimum ON Time
(BMOT)
(RMOT)