CALIFORNIA MICRO DEVICES
CM88L70/70C
Explanation of Events
A)
B)
C)
D)
E)
F)
G)
Tone bursts detected, tone duration invalid, outputs not
updated.
Tone #n detected, tone duration valid, tone decoded and
latched in outputs.
End of tone #n detected, tone absent duration valid,
outputs remain latched until next valid tone.
Outputs switched to high impedance state.
Tone #n + 1 detected, tone duration valid, tone decoded
and latched in outputs (currently high impedance).
Acceptable dropout of tone #n + 1, tone absent duration
invalid, outputs remain latched.
End of tone #n + 1 detected, tone absent duration valid,
outputs remain latched until next valid tone.
Explanation of Symbols
V
IN
ESt
St/GT
Q1-Q4
StD
DTMF composite input signal.
Early Steering Output. Indicates detection
of valid tone frequencies.
Steering input/guard time output. Drives
external RC timing circuit.
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.
Tone Output Enable (input). A low level
shifts Q1-Q4 to its high impedance state.
Maximum DTMF signal duration not
detected as valid.
Minimum DTMF signal duration required
for valid recognition.
Minimum 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.
TOE
t
REC
t
REC
t
ID
t
DO
t
DP
t
DA
t
GTP
t
GTA
©2000 California Micro Devices Corp. All rights reserved.
4
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
8/16/2000
CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
