V.22 bis Modem with AT Commands
CMX866
DTMF Decoder
Notes
Min.
Typ.
Max.
Unit
Valid input signal levels
(each tone of composite signal)
10
10
-30.0
-
0.0
dBm
Not decode level
(either tone of composite signal)
Twist = High Tone/Low Tone
Frequency Detect Bandwidth
Frequency Not Detect Bandwidth
Max level of low frequency noise (i.e dial tone)
Interfering signal frequency <= 550Hz
Interfering signal frequency <= 450Hz
Interfering signal frequency <= 200Hz
Max. noise level wrt. signal
DTMF detect response time
DTMF de-response time
Status Register b5 high time
‘Will Detect’ DTMF signal duration
‘Will Not Detect’ DTMF signal duration
Pause length detected
-
-
-
-
-
-36.0
6.0
-
dBm
dB
%
-10.0
±1.8
-
±3.5
%
14
14
14
-
-
-
-
-
-
-
-
-
-
-
-
-
-
0.0
10.0
20.0
-10.0
40.0
30.0
-
-
-
-
dB
dB
dB
dB
ms
ms
ms
ms
ms
ms
ms
14,15
14.0
40.0
-
30.0
-
25.0
-
-
Pause length ignored
15.0
Notes:
1. At 25°C, not including any current drawn from the CMX866 pins by external circuitry
other than X1, C1 and C2.
2. All logic inputs at VSS except for RT, DTRN and RTSN inputs which are at DVDD
3. DSP is powered up but in a reset state.
.
4. Excluding RD and RT pins.
5. % carrier frequency accuracy is the same as XTAL/CLOCK % frequency accuracy.
6
Tx signal % baud or bit rate accuracy is the same as XTAL/CLOCK % frequency
accuracy.
7. Measured between TXA and TXAN pins with Tx Level Control gain set to 0dB, 1k2W load
between TXA and TXAN, at VDD = 3.0V (levels are proportional to VDD - see section
1.4.2). Level measurements for all modem modes are performed with random
transmitted data and without any guard tone. 0dBm = 775mVrms.
8. Measured on the 2 or 4-wire line using the line interface circuits described in section
1.4.2 with the Tx line signal level set to -10dBm for QAM, DPSK, FSK or single tones, -
6dBm and -8dBm for DTMF tones. Excludes any distortion due to external components
such as the line coupling transformer.
9. These are the bit and baud rates of the line signal, the acceptable tolerance is ±0.01%.
10. Rx 2 or 4-wire line signal level assuming 1dB loss in line coupling transformer with Rx
Gain Control block set to 0dB and external components as section 1.4.2.
11. Thresholds and times measured with random data for QAM and DPSK modes,
continuous binary ‘1’ for all FSK modes. Fixed compromise line equaliser enabled.
Signal switched between off and -33dBm
12. ‘Typical’ value refers to 2100Hz or 2225Hz signal switched between off and -33dBm.
Times measured with respect to the received line signal
13. ‘Typical’ values refers to 400Hz signal switched between off and -33dBm
14. Referenced to DTMF tone of lower amplitude.
15. Flat Gaussian Noise in 300-3400Hz band.
16. For V.23r (Tx1200/Rx75) and Bell 202r (Tx1200/Rx150) the calling modem carrier detect
time is typically 1700ms.
ã 2004 CML Microsystems Plc
49
D/866/4
CMLMICRO [ CML MICROCIRCUITS ]
