z02201 ZiLOG Semiconductor, z02201 Datasheet - Page 58

• Manufacturer Part Number: z02201
• Description: Z02201 V.22bis Data Pump With Integrated Afe
• Manufacturer: ZiLOG Semiconductor

Call-Progress Monitoring Using Biquad Tone Detectors
PS000904-0107
The data pump contains two biquad tone detectors that are capable of detecting
energy in a frequency band. These detectors are useful for call-progress
monitoring, where the exact frequency of the incoming signal is not known. Each
biquad tone detector is composed of two cascaded, independently
programmable, biquad sections. The order of biquad coefficients in RAM is:
b2, b1, a3, a2, a1, B2, B1, A3, A2, A1
The addresses for the coefficients for the two sections start at
015FH
The transfer equation for each section of the biquad tone detector is of the form:
There are two threshold settings affecting both biquad tone detectors. The loca-
tions BIQUADOFFTHRESH and BIQUADONTHRESH define the on and off hystere-
sis points where level is in dBm:
1. BIQUADOFFTHRESH–
2. BIQUADONTHRESH–
Use the following formula to set the thresholds:
The default values are –35 dBm (BiQuadOnThresh) and –42dBm (BiQuad-
OffThresh).
The biquad tone detector status is contained in TONESTATUS, bit
TONESTATUS, bit
depends on the coefficients and the input signal frequency.
The biquad tone detectors can be cascaded to form one tone detector with 4
biquad sections (an 8th order IIR filter) by setting ToneStatus.CASCADE. In this
case, TONESTATUS, bit
detector, and TONESTATUS, bit
tone detector B is squared before being input to biquad tone detector A.
The default settings for the biquad tone detector coefficients are indicated in
Table 22
TONEB. The data pump sets the biquad tone detector coefficients to their default
settings at any reset.
(TONEB). The sample rate is 9600 Hz.
and
Table
Threshold
14
H
23, where the first row is TONEA and the second row is
n
(TONEB). The response time of the biquad tone detectors
=
15
051h
2 a
----------------------------------------------------- -
(
052h
1 2b
(
(TONEA) contains the status of the cascaded tone
–
=
1
–ON point.
–OFF point.
+
10
5
a
1
(SQRDIS) controls whether the output of biquad
(
Z
2
level
Z
1 –
1 –
–
) 20
V.22BIS Data Pump with Integrated AFE
+
2b
⁄
a
3
2
⋅
Z
Z
32767
2 –
2 –
)
)
0155H
15
(TONEA) and
(TONEA) and
54