FEDL7020-02
1
Semiconductor
ML7020
tba
tc
tbb
tl
tp
ts
DTMF signal
tg
td
DTMF receive data
SP
tsp
Figure 3 DTMF reception timing
ts: Input signal persistence duration (detection)
Normal reception is made when the input signal persistence duration is equal to ts or more.
tI: Input signal persistence duration (non-detection)
The input signal is ignored when the input signal persistence duration is less than tI, and the SP and DTMF
receive data are not output.
tp: Signal quiet duration
The DTMF receive data and SP are reset if the input continues to be in the no-signal condition for a
duration equal to tp or longer.
Also, even if the receive data changes during DTMF signal reception, SP continues to be “1” and the
DTMF receive data may remain in the initial value and may not change, if the signal quiet duration is less
than tp (including when it changes without any instantaneous break).
tba: Instantaneous break protection period 1
This is applicable to the period after the input signal has arrived and until the timing when SP becomes “1”.
In other words, SP and DTMF receive data are output normally even if a no-signal condition of a duration
less than tba occurs.
tbb: Instantaneous break protection period 2
This is applicable when SP is “1” (during output of the receive data). In other words, SP and the DTMF
receive data are not reset even if a no-signal condition of a duration less than tbb occurs during signal
reception.
tc: For ensuring normal reception, make sure that the signal repetition period is equal to tc or more.
tg: Detection delay time
The DTMF receive data is output with a delay of tg relative to the appearance of the input signal.
td: Detection hold time
The output of SP or the DTMF receive data is stopped with a delay of td after the termination of the input
signal.
tsp: SP delay time
SP is output after a delay of tsp relative to the output of the DTMF receive data. Therefore, latch the
DTMF receive data when the rising edge of SP is detected.
10/19
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