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Z02202
ZiLOG
V.22bis Data Pump with Integrated AFE
PS000902-0501
Z02201
35
TONESTATUS
, bit
15
(
TONEA
) contains the status of the
cascaded tone detector, and
TONESTATUS
, bit
5
(
SQRDIS
) controls whether the output of biquad 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 17 and Table 18, where the first row
is
TONEA
and the second row is
TONEB
. The data pump
sets the biquad tone detector coefficients to their default
settings at any reset.
To use the Biquad tone detectors to perform Call-Progress
Monitoring, execute the following:
1. Set the coefficients. Coefficients which are changed
remain valid until the next reset.
2. Set
CONFIG
register, bits 0–6 (
MODE
) to
2
(detect
tones). The biquad tone detectors and the discrete tone
detectors operate simultaneously to allow the host to
look for call-progress tones and individual answer
tones at the same time.
3. Set
the
BIQUADONTHRESH
and
BIQUADOFFTHRESH
values.
4. If the two biquad tone detectors are to be cascaded,
set
TONESTATUS
, bit
13
(
CASCADE
) to
1
. If
required, set
TONESTATUS
, bit
5
(
SQRDIS
)
to
1
to
disable the squarer when the tone detectors are
cascaded.
5.
Inspect
TONESTATUS
, bit
15
(
TONEA
) and
TONESTATUS
, bit
14
(
TONEB
) for the detection
status. If
TONESTATUS
, bit
13
(
CASCADE
)
is set,
only inspect
TONESTATUS
, bit
15
(
TONEA
).
6. Time the ON time and the OFF time of the tone(s) to
provide the cadence, which is used to identify the type
of call-progress tone detected.After call-progress
monitoring is complete, set
CONFIG
register, bits 0–6
(
MODE
) to
0
(
STANDBY
).
SIMULTANEOUS TRANSMISSION AND DETECTION OF TONES
Setting
CONFIG
register, bits 0–6 (
MODE
) to
4
enables the
simultaneous operation of all Discrete Tone Detectors,
Biquad Tone Detectors, and Tone Generators. Please refer
to the sections “Transmitting Tones”, “Tone Detectors” and
“” for descriptions of how to use each of these features by
itself.
The host uses simultaneous transmission and detection of
tones when it needs to detect tones while generating a single
tone. An example during the call establishment phase of a
special purpose modem.
To prevent a single generated tone from interfering with the
tone detectors the host programs data pump RAM locations
0x1A2 through 0x1A6 with coefficients for a notch filter
to remove a single tone from the received signal used by
the tone detectors.
The notch filter coefficients are set to their default values
when the host sets
CONFIG
register, bits 0–6 (
MODE
) to
4
, so the host writes new values to these locations after
setting
CONFIG
register, bits 0–6 (
MODE
) to begin
simultaneous transmission and detection of tones. The
default notch filter coefficient values cause the notch filter
to not change the received signal used by the tone detectors.
The notch filter is a biquad section (2nd-order IIR filter).
The values of the coefficients determine the frequency to
be removed. Refer to the description of RAM location
“Notch” for the formulae used to compute these commonly
used coefficient values:
Table 17. Biquad Section 1 Coef
fi
cients (Hex)
Band (Hz)
245–650
360
–
440
b2
C774
C148
b1
7601
7A66
a3
0716
FF5C
a2
a1
F5FB
0000
0716
00A4
Table 18. Biquad Section 2 Coef
fi
cients (Hex)
Band (Hz)
245
–
650
360
–
440
B2
C63E
C7CD
B1
6FE1
7438
A3
F8EA
01AA
A2
0000
FEBC
A1
0716
01AA