mt88l89asr1 Zarlink Semiconductor, mt88l89asr1 Datasheet - Page 7

• Manufacturer Part Number: mt88l89asr1
• Description: 3 V Integrated Dtmf Transceiver With Adaptive Micro Interface
• Manufacturer: Zarlink Semiconductor

The value of t
to be recognized by the receiver. A value for C1 of 0.1 µF is recommended for most applications, leaving R1 to be
selected by the designer. Different steering arrangements may be used to select independent tone present (t
and tone absent (t
and reject limits on tone duration and interdigital pause. Guard time adjustment also allows the designer to tailor
system parameters such as talk-off and noise immunity.
Increasing t
maintain a valid signal condition long enough to be registered. Alternatively, a relatively short t
would be appropriate for extremely noisy environments where fast acquisition time and immunity to tone drop-outs
are required. Design information for guard time adjustment is shown in Figure 6. The receiver timing is shown in
Figure 7 with a description of the events in Figure 8.
V
ESt
St/GT
RX
b3
b2
Read
Status
Register
IRQ/CP
in
EVENTS
0
-RX
3
REC
DP
improves talk-off performance since it reduces the probability that tones simulated by speech will
is a device parameter (see AC Electrical Characteristics) and t
t
REC
GTA
DECODED TONE # (n-1)
) guard times. This may be necessary to meet system specifications which place both accept
A
t
DP
Figure 7 - Receiver Timing Diagram
t
Zarlink Semiconductor Inc.
REC
TONE #n
MT88L89
B
t
GTP
7
t
PStRX
t
PStb3
t
# n
ID
C
t
DA
t
GTA
TONE
#n + 1
D
REC
t
DO
is the minimum signal duration
E
TONE
#n + 1
# (n + 1)
REC
with a long t
Data Sheet
F
V
TSt
GTP
DO
)