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application note st75c520 - a complete dtmf detection checking from revision 1.2 to revision 1.4 AN920/0597 contents page 1 introduction ....................................................... 1 2 dtmf detection requirements ...................................... 2 3 measurements conditions ......................................... 2 4 glossary .......................................................... 2 4.1 the three st75c520 set-up modes in dtmf detection. . . . . . . . . ................ 2 4.2 the three comments . . . . . . . . . . . . . . . . . . . . . . ............................. 2 5 how to use the dtmf detection report ............................ 2 6 measurements with revision 1.3 - nominal frequencies ............. 3 6.1 nominal frequencies, no twist - default mode . . . . . . .......................... 3 6.2 nominal frequencies, no twist - frozen gain - new 852hz filter - new thresholds. . . . . . 3 6.3 nominal frequencies, no twist - analog gain time constant low . . . . . . . . . . . . . . . . . . 3 7 measurements with revision 1.4 - nominal frequencies ............. 4 7.1 nominal frequencies, no twist - default mode. . . . . . . . . . . . . . . . . . . . . . . .......... 4 7.2 nominal frequencies, no twist - analog gain frozen . . . . . . . . . ................... 4 7.3 frequencies, no twist - analog gain time constant low. . . . . . .................... 4 8 measurement with revision 1.3 - frequency offset 1.5% ............ 5 8.1 frequency offset 1.5% , no twist - default mode . . . . . . . . . . . . . . . . . . . . . . . ....... 5 8.2 frequency offset 1.5% , no twist - analog gain frozen, new 852hz filter, new thresholds . ....................................................... 6 8.3 frequency offset 1.5% , no twist - analog gain time constant low . . . . . . . . . ....... 7 9 measurement with revision 1.4 - frequency offset 1.5% ............ 8 9.1 frequency offset 1.5% , 6db of twist - default mode . . . . . . . . . . . . . . . . . . . . . . . .... 8 9.2 frequency offset 1.5% , 6db of twist - analog gain frozen . . . . . . . . . ............. 9 9.3 frequency offset 1.5% , 6db of twist - analog gain time constant low . . . . . . . . . .... 10 10 conclusion ........................................................ 11 1 - introduction in this application note is described various dtmf detection tests done with revision 1.3 and revision 1.4 of the st75c520. the aim of this document is to show the performances of the dtmf detection function and the benefits the revision 1.4 gives. 1/11
2 - dtmf detection requirements hereafterare describedthe test conditionsused for the dtmf performance measurements : - level of dtmf signal at rxa pin : 4.5dbm to 39.5dbm - twist : 6db. - frequency offset : 1.5% - dtmf application : t on (ms) t off (ms) nature of the test 55 45 detection fiability 150 65 detection fiability and sta_dtmf stability 500 500 3 - measurements conditions the level of dtmf digits is measured on the line. because there is an attenuation of -4.5db on our daa, we check that level from 0dbm to -35dbm. we are using on the line a current loop of 30ma to simulate telephone conditions. for the dynamic tests, we use the following sequencesent automat- ically by the hp8904a multifunction synthesizer dc- 600khz : 123456789abcd*#123456... the dynamic tests are done in part 1 and 2. the static test with frequency offset are done in part 3 and 4. please note that all the measures done for rev 1.3 are valid for rev 1.2. and all the measures done for rev 1.4 are valid for the future rev 1.5. in order to meet 0dbm on the line with 6db of twist, the componant must detect dtmf digits with -1dbm of magnitude(because one -1dbm and one -7dbm sine componant give a 0dbm signal on the line). however, sgs-thomson only guarantees two -3dbm sine amplitude because of the limited detection dynamic of the st75c520. in order to meet -35dbm on the line with 6db of twist, the componant must detect dtmf digits with -42dbm of magnitude (because one -42dbm and one -36dbm sine componant give a -35dbm signal on the line). that condition is met with revision 1.4 and is limited to two -38dbm sine amplitude in revisqion 1.2 and 1.3. 4 - glossary 4.1 - the three st75c520 set-up modes in dtmf detection for each part you will find three different para- graphs that correspond to three programmation mode for the st75c520 : - the default mode : for rev 1.2 and 1.3, nothing is added.for rev 1.4, some memory writes have been added in order to meet the requirements (by default, rev 1.4 detects from -1dbm to -35dbm with a good speech immunity) : mw 4a 13 89 05 1db attenuation for the 1209hz filter mw f2 17 00 14 comparaison threshold between 1209 and 1336hz mw f4 17 00 14 comparaison threshold between 1336 and 1477hz mw f5 17 00 14 comparaison threshold between 1336 and 1209hz mw 2e 12 60 00 lower threshold for low pass filter mw 2f 12 60 00 lower threshold for high pass filter - the analog gain frozen mode : in that mode, the analog gain is frozen : mw d2 17 02 00 analog gain frozen conf 04 dtmf detection enable for rev 1.2 and 1.3, youhave to use after conf command the followingsequencein order to keep the detection dynamic : mw ea 12 a5 0a lowpass gain mw 02 13 5e 65 hipass gain mw 2e 12 e0 00 higher threshold for low pass filter mw 2f 12 e0 00 higher threshold for high pass filter mw 1a 13 8a 02 gain for 697hz filter mw 26 13 30 03 gain for 770hz filter mw 32 13 00 02 gain for 852hz filter mw 3e 13 40 04 gain for 941hz filter - the analog gain time constant low : in that mode, the time constant of the analog gain is lowered in order to avoid sta_dtmf instability : conf 04 dtmf detection enable mw de 17 00 f0 analog gain time constant low 4.2 - the three comments you will find three differentcomments on the follow- ing tables : - false digits : some digits has been added during the test. - digits not detected or no detect : some digits are not detected or no digits are detected at all. - ok : all digits sent by the generator during the test have beendetectedwith no loss and no addeddigits. 5 - how to use the dtmf detection report the tables used in part 2 and 3 describes dtmf detection with four t on /t off cases (continue,55/45, 150/65, 500/500). the tables used in part 4 and 5 describes dtmf detection with 1.5% of frequency offset and 6db of twist. each digit is described with two frequencies: f low and f high . and when we test +1.5% on one frequency, we have chosen to keep the other nominal. thus for examplethe result of the status f low use a 1.5% offset for f low and a nominal value for f high . hereunderis rememberedthe nominal frequencies of the dtmf digits : 697hz 770hz 852hz 941hz 1209hz 147* 1336hz 2580 1477hz 369# 1633hz abcd st75c520 revision 1.4 dtmf detection report 2/11
6 - measurements with revision 1.3 - nominal frequencies 6.1 - nominal frequencies, no twist - default mode line level (db) continue 55/45 150/65 500/500 0 ok ok ok ok -5 ok ok ok ok -10 ok ok ok ok -15.5 false * false digits false digits false * -19.5 ok ok ok ok -26 ok ok ok ok -29 ok ok ok ok -35 false * ok false digits false digits 6.2 - nominal frequencies, no twist - frozen gain - new 852hz filter - new thresholds line level (db) continue 55/45 150/65 500/500 0 ok ok ok ok -5 ok ok ok ok -10 ok ok ok ok -15.5 ok ok ok ok -19.5 ok ok ok ok -26 ok ok ok ok -29 ok ok ok ok -35 digits not detected digits not detected digits not detected digits not detected 6.3 - nominal frequencies, no twist - analog gain time constant low line level (db) continue 55/45 150/65 500/500 0 ok ok ok ok -5 ok ok ok ok -10 ok ok ok ok -15.5 ok ok ok ok -19.5 ok ok ok ok -26 ok ok ok ok -29 ok ok ok ok -35 false digits ok false digits false digits st75c520 revision 1.4 dtmf detection report 3/11
7 - measurements with revision 1.4 - nominal frequencies 7.1 - nominal frequencies, no twist - default mode line level (db) continue 55/45 150/65 500/500 0 ok ok ok ok -5 ok ok ok ok -10 ok ok ok ok -15.5 false * ok ok false * -19.5 ok ok ok ok -26 ok ok ok ok -29 ok ok ok ok -35 ok ok ok ok 7.2 - nominal frequencies, no twist - analog gain frozen line level (db) continue 55/45 150/65 500/500 0 ok ok ok ok -5 ok ok ok ok -10 ok ok ok ok -15.5 ok ok ok ok -19.5 ok ok ok ok -26 ok ok ok ok -29 ok ok ok ok -35 ok ok ok ok 7.3 - frequencies, no twist - analog gain time constant low line level (db) continue 55/45 150/65 500/500 0 ok ok ok ok -5 ok ok ok ok -10 ok ok ok ok -15.5 ok ok ok ok -19.5 ok ok ok ok -26 ok ok ok ok -29 ok ok ok ok -35 ok ok ok ok st75c520 revision 1.4 dtmf detection report 4/11
8 - measurement with revision 1.3 - frequency offset 1.5% 8.1 - frequency offset 1.5% , no twist - default mode level (dbm) f low (hz) f high (hz) status f low status f high digit * 0 955 (+1.5%) 1227 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false * false * -19.5 ok ok -25.5 ok ok -29 false * false * -35 ok ok 0 927 (-1.5%) 1191 (-1.5%) ok ok -5 false * ok -9.5 false * ok -15.5 false * false * -19.5 false * ok -25.5 false * ok -29 false * false * -35 false * false * digit 8 0 865 (+1.5%) 1356 (+1.5%) ok ok -5 false 8 ok -9.5 false 8 ok -15.5 false 8 ok -19.5 false 8 ok -25.5 false 8 false 8 -29 false 8 false 8 -35 false 8 false 8 0 839 (-1.5%) 1316 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 false 8 false 8 -29 false 8 false 8 -35 ok false 8 level (dbm) f low (hz) f high (hz) status f low status f high digit 6 0 782 (+1.5%) 1499 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false 6 ok -19.5 false 6 ok -25.5 false 6 ok -29 false 6 false 6 -35 false 6 false 6 0 758 (-1.5%) 1455 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 false 6 ok -29 false 6 false 6 -35 false 6 false 6 digit a 0 708 (+1.5%) 1658 (+1.5%) false a ok -5 false a ok -9.5 false a ok -15.5 false a ok -19.5 false a ok -25.5 false a ok -29 false a false a -35 false a false a 0 686 (-1.5%) 1608 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 false a ok -25.5 ok ok -29 false a false a -35 false a false a st75c520 revision 1.4 dtmf detection report 5/11
8.2 - frequency offset 1.5% , no twist - analog gain frozen, new 852hz filter, new thresholds 8 - measurement with revision 1.3 - frequency offset 1.5% (continued) level (dbm) f low (hz) f high (hz) status f low status f high digit * 0 955 (+1.5%) 1227 (+1.5%) ok false * -5 ok ok -9.5 ok ok -15.5 ok false * -19.5 ok ok -25.5 ok ok -29 ok ok -35 false * false * 0 927 (-1.5%) 1191 (-1.5%) no detect false * -5 false * ok -9.5 false * ok -15.5 false * ok -19.5 false * ok -25.5 false * ok -29 false * ok -35 false * false * digit 8 0 865 (+1.5%) 1356 (+1.5%) false 8 false 8 -5 false 8 ok -9.5 false 8 ok -15.5 false 8 false 8 -19.5 false 8 false 8 -25.5 false 8 ok -29 false 8 ok -35 false 8 false 8 0 839 (-1.5%) 1316 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false 8 false 8 -19.5 false 8 false 8 -25.5 false 8 ok -29 ok ok -35 false 8 false 8 level (dbm) f low (hz) f high (hz) status f low status f high digit 6 0 782 (+1.5%) 1499 (+1.5%) no detect false 6 -5 false 6 ok -9.5 false 6 ok -15.5 false 6 false 6 -19.5 false 6 ok -25.5 false 6 ok -29 false 6 ok -35 false 6 false 6 0 758 (-1.5%) 1455 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false 6 false 6 -19.5 false 6 ok -25.5 false 6 ok -29 ok ok -35 false 6 false 6 digit a 0 708 (+1.5%) 1658 (+1.5%) no detect ok -5 false a ok -9.5 false a ok -15.5 false a false a -19.5 false a ok -25.5 false a false a -29 false a ok -35 false a false a 0 686 (-1.5%) 1608 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false a false a -19.5 false a false a -25.5 false a false a -29 ok ok -35 ok false a st75c520 revision 1.4 dtmf detection report 6/11
8.3 - frequency offset 1.5% , no twist - analog gain time constant low 8 - measurement with revision 1.3 - frequency offset 1.5% (continued) level (dbm) f low (hz) f high (hz) status f low status f high digit * 0 955 (+1.5%) 1227 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 false * false * -35 false * false * 0 927 (-1.5%) 1191 (-1.5%) false * ok -5 false * ok -9.5 false * ok -15.5 false * ok -19.5 false * ok -25.5 false * ok -29 false * false * -35 false * false * digit 8 0 865 (+1.5%) 1356 (+1.5%) false 8 ok -5 false 8 ok -9.5 false 8 ok -15.5 false 8 ok -19.5 false 8 ok -25.5 false 8 false 8 -29 false 8 false 8 -35 false 8 false 8 0 839 (-1.5%) 1316 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 false 8 false 8 -29 false 8 false 8 -35 false 8 false 8 level (dbm) f low (hz) f high (hz) status f low status f high digit 6 0 782 (+1.5%) 1499 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false 6 ok -19.5 false 6 ok -25.5 false 6 ok -29 false 6 false 6 -35 false 6 false 6 0 758 (-1.5%) 1455 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 false 6 ok -29 false 6 false 6 -35 false 6 false 6 digit a 0 708 (+1.5%) 1658 (+1.5%) false a ok -5 false a ok -9.5 false a ok -15.5 false a ok -19.5 false a ok -25.5 false a ok -29 false a false a -35 false a false a 0 686 (-1.5%) 1608 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 false a ok -25.5 ok ok -29 false a false a -35 false a false a st75c520 revision 1.4 dtmf detection report 7/11
9 - measurement with revision 1.4 - frequency offset 1.5% 9.1 - frequency offset 1.5% , 6db of twist - default mode level (dbm) f low (hz) f high (hz) status f low status f high digit * 0 955 (+1.5%) 1227 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 false * ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 927 (-1.5%) 1191 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok false * -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok digit 8 0 865 (+1.5%) 1356 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 839 (-1.5%) 1316 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok level (dbm) f low (hz) f high (hz) status f low status f high digit 6 0 782 (+1.5%) 1499 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 758 (-1.5%) 1455 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok digit a 0 708 (+1.5%) 1658 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 686 (-1.5%) 1608 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok st75c520 revision 1.4 dtmf detection report 8/11
9.2 - frequency offset 1.5% , 6db of twist - analog gain frozen 9 - measurement with revision 1.4 - frequency offset 1.5% (continued) level (dbm) f low (hz) f high (hz) status f low status f high digit * 0 955 (+1.5%) 1227 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 927 (-1.5%) 1191 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok digit 8 0 865 (+1.5%) 1356 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 839 (-1.5%) 1316 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok level (dbm) f low (hz) f high (hz) status f low status f high digit 6 0 782 (+1.5%) 1499 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 758 (-1.5%) 1455 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok digit a 0 708 (+1.5%) 1658 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 686 (-1.5%) 1608 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok st75c520 revision 1.4 dtmf detection report 9/11
9.3 - frequency offset 1.5% , 6db of twist - analog gain time constant low 9 - measurement with revision 1.4 - frequency offset 1.5% (continued) level (dbm) f low (hz) f high (hz) status f low status f high digit * 0 955 (+1.5%) 1227 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 927 (-1.5%) 1191 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok digit 8 0 865 (+1.5%) 1356 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 839 (-1.5%) 1316 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok level (dbm) f low (hz) f high (hz) status f low status f high digit 6 0 782 (+1.5%) 1499 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 758 (-1.5%) 1455 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok digit a 0 708 (+1.5%) 1658 (+1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok 0 686 (-1.5%) 1608 (-1.5%) ok ok -5 ok ok -9.5 ok ok -15.5 ok ok -19.5 ok ok -25.5 ok ok -29 ok ok -35 ok ok st75c520 revision 1.4 dtmf detection report 10/11
information furni shed is believed to be accurate and reliable. however, sgs-thomson micr oelectronics 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 und erany patent or patent rights of sgs-thomson microelectronics. specifications mentioned in this publication are subject to change without notice. this pu blication 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. ? 1997 sgs-thomson microelectronics - all rights reserved purchase of i 2 c components of sgs-thomson microelectronics, conveys a license under the philips i 2 c patent. rights to use these components in a i 2 c system, is granted provided that the system conforms to the i 2 c standard specifications as defined by philips. sgs-thomson microelectronics group of companies australia - brazil - canada - china - france - germany - hong kong - italy - japan - korea - malaysia - malta - morocco the netherlands - singapore - spain - sweden - switzerland - taiwan - thailand - united kingdom - u.s.a. 10 - conclusion it is clear in this document that the revision 1.4 is more efficient in dtmf detection field than revision 1.3. in addition, sgs-thomson pro- poses some memory writes (see paragraph 3.1 page 2) in order to further improve revision 1.4 behaviour toward frequency offset. anyway, per- harps the customer will find that revision 1.3 is not goodenoughwith 1.5% offrequencyoffset. but sgs-thomson points out that revision 1.3 should work with less drastic specifications (1% only for example). to conclude, we hope that re- vision 1.3 will meet your basic specifications and revision 1.4 will content all your requirements in dtmf detection st75c520 revision 1.4 dtmf detection report 11/11

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