MT8870 View Datasheet(PDF) - Mitel Networks
Part Name
Description
Manufacturer
MT8870 Datasheet PDF : 12 Pages
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ISO2-CMOS MT8870D/MT8870D-1
EVENTS
Vin
ESt
St/GT
Q1-Q4
StD
TOE
A
tREC
D
B
C
E
F
G
tREC
tID
tDO
TONE #n
TONE
#n + 1
tDP
AAAAAAAA
tDA
tGTP
tGTA
TONE
#n + 1
tPQ
DECODED TONE # (n-1)
tPSrD
tQStD
#n
HIGH IMPEDANCE
# (n + 1)
tPTD
tPTE
VTSt
EXPLANATION OF EVENTS
A)
TONE BURSTS DETECTED, TONE DURATION INVALID, OUTPUTS NOT UPDATED.
B)
TONE #n DETECTED, TONE DURATION VALID, TONE DECODED AND LATCHED IN OUTPUTS
C)
END OF TONE #n DETECTED, TONE ABSENT DURATION VALID, OUTPUTS REMIAN LATCHED UNTIL NEXT VALID
TONE.
D)
OUTPUTS SWITCHED TO HIGH IMPEDANCE STATE.
E)
TONE #n + 1 DETECTED, TONE DURATION VALID, TONE DECODED AND LATCHED IN OUTPUTS (CURRENTLY
HIGH IMPEDANCE).
F)
ACCEPTABLE DROPOUT OF TONE #n + 1, TONE ABSENT DURATION INVALID, OUTPUTS REMAIN LATCHED.
G)
END OF TONE #n + 1 DETECTED, TONE ABSENT DURATION VALID, OUTPUTS REMAIN LATCHED UNTIL NEXT
VALID TONE.
EXPLANATION OF SYMBOLS
Vin
DTMF COMPOSITE INPUT SIGNAL.
ESt
EARLY STEERING OUTPUT. INDICATES DETECTION OF VALID TONE FREQUENCIES.
St/GT STEERING INPUT/GUARD TIME OUTPUT. DRIVES EXTERNAL RC TIMING CIRCUIT.
Q1-Q4
StD
4-BIT DECODED TONE OUTPUT.
DELAYED STEERING OUTPUT. INDICATES THAT VALID FREQUENCIES HAVE BEEN PRESENT/ABSENT FOR THE
REQUIRED GUARD TIME THUS CONSTITUTING A VALID SIGNAL.
TOE
tREC
tRE C
tID
tDO
tDP
tDA
tGTP
tGTA
TONE OUTPUT ENABLE (INPUT). A LOW LEVEL SHIFTS Q1-Q4 TO ITS HIGH IMPEDANCE STATE.
MAXIMUM DTMF SIGNAL DURATION NOT DETECED AS VALID
MINIMUM DTMF SIGNAL DURATION REQUIRED FOR VALID RECOGNITION
MAXIMUM TIME BETWEEN VALID DTMF SIGNALS.
MAXIMUM ALLOWABLE DROP OUT DURING VALID DTMF SIGNAL.
TIME TO DETECT THE PRESENCE OF VALID DTMF SIGNALS.
TIME TO DETECT THE ABSENCE OF VALID DTMF SIGNALS.
GUARD TIME, TONE PRESENT.
GUARD TIME, TONE ABSENT.
Figure 11 - Timing Diagram
4-21
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