at75c1222 ETC-unknow, at75c1222 Datasheet - Page 13

• Manufacturer Part Number: at75c1222
• Manufacturer: ETC-unknow

DTMF Detection Configuration
Request
DTMF Detection Start Request DTMF detection is started as soon as the DSP unit receives the DTMF detection start
DTMF Detection Stop Request DTMF detection is stopped as soon as the DSP unit receives the DTMF detection stop
2664A–INTAP–07/02
Table 18. DTMF Detection Configuration Request
Example: 0x0009 0x0830 0x0020 0x0020 0x2000 0x2000 0x4000 0x4000 0x001E
0x001E:
This message configures the DTMF detector with a detection level of 33 dB below the
reference level for each group. The minimum difference level between the strongest fre-
quency in a group and the others of the same group must be at least of 18 dB. The
maximum difference level between the two groups must be at most 12 dB. In order to
recognize a character, the signal must last for a minimum of 30 ms and then be followed
by 30 ms of silence.
request.
Table 19. DTMF Detection Start Request
request.
Table 20. DTMF Detection Stop Request
Word 0
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Word 8
Word 9
Word 0
Word 1
Word 0
Word 1
DTMFDET_HIGHTHRES
DTMFDET_LOWTHRES
DTMFDET_ NEGTWIST
DTMFDET_POSTWIST
DTMFDET_DURATION
DTMFDET_HIGHREL
= 65535 * 10E(dB/10)
DTMFDET_SILENCE
DTMFDET_LOWREL
= 65535* 10E(dB/10)
= 65535* 10E(dB/20)
= 65535* 10E(dB/20)
= 65535* 10E(dB/10)
= 65535* 10E(dB/10)
0x0009
0x0830
0x0001
0x0831
0x0001
0x0832
Message length = 0x0001
Request ID = 0x0831
Message length = 0x0001
Request ID = 0x0832
Message length = 0x0009
Request ID = 0x0830
Low Group Power Detection Threshold (default: -
40dB)
High Group Power Detection Threshold (default: -
40dB)
Minimum difference level between the strongest
frequency in the low group and the other of the
same group (default: -20dB)
Minimum difference level between the strongest
frequency in the high group and the other of the
same group (default: -20dB)
Maximum Low to High twist
(default: -8dB)
Maximum High to Low twist
(default: -8dB)
Duration of signal condition for character
recognition in milliseconds
(default: 30 ms).
Duration of silence condition for character
recognition in milliseconds (default: 30 ms).
AT75C1222
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