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APPLICATION NOTE
ST75C502 - DEFAULT TONE DETECTORS
1 - INTRODUCTION The purpose of this application note is to describe the default setup for the tone detection, and the way they are managed during the Automode Handshake. Refer to ST75C502 for explanation of the Tone detectors. The 16 cells of the tone detectors are used, by the ST75C502, for various functions. The internal variable _NTDCELL define the number of tone detectors currently executed by the DSP. This number is set to 16 after a RESET, and will be set to 0 as soon as the Autobaud phase is completed. The Autobaud Handshake is complete when we perfectly know the transmission standard. While configuring for DTMF Detection, the upper 12 cells are overwritten to detect the 8 DTMF tones, plus 4 cells to split the band for differentiate Low group and High group of tones. Refer to the Appendix for the default wiring of the tone detector. 2 - CELL DESCRIPTION The First cell (#0) is programmed as a 440Hz tone detector (Call Waiting Detection) and is never changed whatever the DSP is doing. After a RESET (or init command) or any conf command, its parameters are set to detect the 440Hz single tone. The template of this Tschebyscheff filter is :
Name CALLWAIT Cell Number 0 Type Band Pass Pass Band (Hz) 430, 450 Stop Band (Hz) 340, 540 Ripple (dB) 0.1 Reject (dB) 25
The second and third cell (#1 and #2) are used for Call progress detection. It is a Low pass filter with a cutoff frequency of 650 Hz. this filter like the previous one is never changed. The template of this Tschebyscheff filter is :
Name CPLOW Cell Number 1, 2 Type Low Pass Pass Band (Hz) 0, 650 Stop Band (Hz) 1000 Ripple (dB) 0.2 Reject (dB) 45
Due to the DAA implementation and to the ST7544 analog front end receive filter, the frequencies below 300Hz are attenuated. Refer to Measurement Report for the detection area. The cell mumber 3 and 4 are used for Call progress tone detection. It is a High pass filter with a cutoff frequency of 600Hz. The template of this Tschebyscheff filter is :
Name CPHIGH Cell Number 3,4 Type High Pass Pass Band (Hz) 600, 3600 Stop Band (Hz) 400 Ripple (dB) 0.2 Reject (dB) 45
Frequencies above 3200Hz are attenuated due to the DAA and the ST7544 Receive filter. While using the DTMF Mode (with a conf command) the cell 4 to 15 are overwritted with the DTMF detector parameters.
AN537/0595 1/5
ST75C502 - DEFAULT TONE DETECTORS
Starting from cell 5 the following 11 Cells are used for Autobaud Handshake. The default autobaud mode corresponds to the V.32bis Originate mode. While selecting the Answer mode (with a conf command) some cells are overwritten. Cell number 5 and 6 are used to remove from the received signal what we are transmitting. This give a better immunity to noise than regular comparators. The corresponding filters are notch filters to remove the 2100Hz Answer tone in answer mode and the 1800Hz AA V.32bis tone in the originate mode. The templates of these Butterworth filters are :
Mode Orig Answer Name AZ1800 OZ2100 Cell Number 5,6 5,6 Type Notch Notch Pass Band (Hz) 1650, 1950 1950, 2250 Stop Band (Hz) 1780, 1820 2080, 2120 Ripple (dB) 3 3 Reject (dB) 30 30
Cell number 7 and 8 are used to detect the V.32bis AC tone. This signal is composed of a 600Hz and 3000Hz tones. Due to the possible amplitude distortion introduced by the telephone line only the 600Hz is used for AC detector. In Answer mode these cells are not used. The template of this Tchebyscheff filter is :
Name AN600 Cell Number 7, 8 Type Band Pass Pass Band (Hz) 580, 620 Stop Band (Hz) 500, 700 Ripple (dB) 0.3 Reject (dB) 45
Cell number 9 is used to detect the V.23 1300Hz Mark tone in Originate mode and the V.23 390Hz in Answer Mode. The template of these Eliptic filters are :
Mode Orig Answ Name AN1300 ORG390 Cell Number 9 9 Type Band Pass Band Pass Pass Band (Hz) 1275, 1325 360, 420 Stop Band (Hz) 1000, 1600 200, 650 Ripple (dB) 0.5 1 Reject (dB) 45 40
Cell number 10 and 11 are used to detect the V.21 1650Hz Mark tone in originate Mode and V.21 980Hz Mark tone in Answer Mode. The template of these Tchebyscheff filters are :
Mode Orig Answ Name AN1650 ORG980 Cell Number 10,11 10,11 Type Band Pass Band Pass Pass Band (Hz) 1625, 1675 968, 992 Stop Band (Hz) 1500, 1800 900, 1060 Ripple (dB) 0.1 0.05 Reject (dB) 45 45
Cell number 12 and 13 are used to detect CCITT 2100Hz Answer tone while in Originate mode and the V.32bis AA signal (1800Hz) while in Answer mode. The template of these Tchebyscheff filters are :
Mode Orig Name ANS2100 Cell Number 12,13 12,13 Type Band Pass Band Pass Pass Band (Hz) 2080, 2120 1780, 1820 Stop Band (Hz) 2030, 2170 1700, 1900 Ripple (dB) 0.3 0.3 Reject (dB) 45 45
Answer ORG1800
In Originate Mode the Cells number 14 and 15 are used to detect the Bell 212 and Bell 103 Answer 2225Hz Answer tone. This filter covers also the V.22 unscrambled "1" at the beginning of the answer mode handshake. In Answer Mode these cells are used to detect the Bell 103 1270Hz. The template of these Tchebyscheff filters are :
Mode Orig Answ Name ANS2225 ORG1270 Cell Number 14,15 14,15 Type Band Pass Band Pass Pass Band (Hz) 2205, 2270 1250, 1290 Stop Band (Hz) 2140, 2360 1150, 1390 Ripple (dB) 0.5 0.1 Reject (dB) 45 45
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ST75C502 - DEFAULT TONE DETECTORS
3 - BIT DESCRIPTION Refer to the Appendix for the default wiring of the cells The 16 bits output of the tone detectors have the following meaning.
Word 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 Bit 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 440Hz higher than -36dBm wide band signal higher than -27dBm Low Pass signal (650Hz) higher than -36dBm High Pass signal (600Hz) higher than -36dBm Low Pass signal higher than High Pass signal Originate signal without 1800Hz higher than -45dBm V.32bis AC signal higher than -45dBm AC signal higher than wide signal without 1800Hz V.23 1300Hz Mark signal higher than -45dBm V.23 1300Hz signal higher than wide signal without 1800Hz V.21 1650Hz Mark signal higher than -45dBm V.21 1650Hz signal higher than wide signal without 1800Hz CCITT 2100Hz Answer tone higher than -45dBm CCITT signal higher than wide signal without 1800Hz Bell 2225 or Unscrambled Mark higher than -45dBm Bell signal higher than wide signal without 1800Hz not used not used V.23 390Hz Mark signal higher than -41dBm V.23 390Hz signal higher than wide signal without 2100Hz + 4dB V.21 980Hz Mark signal higher than -45dBm V.21 980Hz signal higher than wide signal without 2100Hz V.32bis AA signal (1800Hz) higher than -45dBm V.32bis AA signal higher than wide signal without 2100Hz Bell 103 1270Hz Mark signal higher than -45dBm Bell 103 1270Hz signal higher than wide signal without 2100Hz Answer signal without 2100Hz higher than -45dBm Description
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ST75C502 - DEFAULT TONE DETECTORS
4 - APPENDIX Figure 1
BIQUADRATIC FILTER #0
@10
POWER #0
LEVEL #0
@20
@30
COMP. #0
BIQUADRATIC FILTER #1
@11
POWER #1 LEVEL #1
@21 @31
COMP. #1
BIQUADRATIC FILTER #2
@12
POWER #2 LEVEL #2
@22 @32 COMP. #2
D0
@00
GROUND
BIQUADRATIC FILTER #3
@13
POWER #3 LEVEL #3
@23 @33
COMP. #3
D1 D2
RX SIGNAL
@01
BIQUADRATIC FILTER #4
D3
@14
POWER #4 LEVEL #4 BIQUADRATIC FILTER #5
@24
D4 COMP. #4 D5
D6 D7
@02
2
@34 @03
2
@15
POWER #5 LEVEL #5
@25 @35
COMP. #5
TONEDET0
BIQUADRATIC FILTER #6
@16
POWER #6 LEVEL #6
@26 @36 COMP. #6
@37
LEVEL #7
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AN537-01.EPS
BIQUADRATIC FILTER #7
@17
POWER #7
@27
COMP. #7
ST75C502 - DEFAULT TONE DETECTORS
Figure 2
BIQUADRATIC FILTER #18
@18
POWER #8
@28 @38
COMP. #8
LEVEL #8
BIQUADRATIC FILTER #19
@19
POWER #9 LEVEL #9
@29 @39
COMP. #9
BIQUADRATIC FILTER #A
@1A
POWER #A LEVEL #A
@2A @3A COMP. #A
BIQUADRATIC FILTER #B
@1B
POWER #B LEVEL #B
@2B @3B
COMP. #B
D0 D1
D2 D3
BIQUADRATIC FILTER #C
@1C
POWER #C
@2C @3C COMP. #C
D4
D5
D6
LEVEL #C
BIQUADRATIC FILTER #D
D7
@1D
POWER #D LEVEL #D BIQUADRATIC FILTER #E
@2D @3D COMP. #D
TONEDET1
@1E
POWER #E
@2E @3E
COMP. #E
LEVEL #E
BIQUADRATIC FILTER #F
@1F
@3F LEVEL #F
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No licence is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1994 SGS-THOMSON Microelectronics - All Rights Reserved Purchase of I2C Components of SGS-THOMSON Microelectronics, conveys a license under the Philips I2C Patent. Rights to use these components in a I2C system, is granted provided that the system conforms to the I2C Standard Specifications as defined by Philips. SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - China - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A.
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AN537-02.EPS
POWER #F
@2F
COMP. #F

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