MC145740F 查看數據表（PDF） - Motorola => Freescale
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MC145740F Datasheet PDF : 12 Pages
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TRANSMIT ATTENUATOR/AGC GAIN (A3 – A0)
The A3 – A0 bits determine the analog transmit level of
DTMF tones. The transmit attenuator range is controlled
from 0 to 15 dB in 1 dB steps as shown in Table 3. However,
this attenuator does not affect the external signal source
from DSI. These four bits also determine the AGC amplifier
gain in DTMF receive mode. In normal operation, “automatic”
may be selected so that the receiver’s gain is automatically
adjusted, corresponding to the input signal level.
TRANSMIT TONE FREQUENCY (T3 – T0)
The T3 – T0 bits determine DTMF tone frequencies trans-
mitted from TxA1 and TxA2 in DTMF transmit and analog
loopback mode, and determine the single tone frequency in
single tone mode. Tone frequency assignments for the
T3 – T0 bits are shown in Table 4.
RECEIVED TONE FREQUENCY (D3 – D0)
The D3 – D0 bits provide hexadecimal codes correspond-
ing to detected DTMF tones. Tone frequency assignments
for the D3 – D0 bits are shown in Table 4.
Table 3. Transmit Attenuator/AGC Gain Set Truth Table
A3
A2
A1
A0
Tx Attenuation (dB)
Rx AGC Gain (dB)
0
0
0
0
0
– 5.0
0
0
0
1
1
– 2.5
0
0
1
0
2
0.0
0
0
1
1
3
2.5
0
1
0
0
4
5.0
0
1
0
1
5
7.5
0
1
1
0
6
10.0
0
1
1
1
7
12.5
1
0
0
0
8
15.0
1
0
0
1
9
17.5
1
0
1
0
10
20.0
1
0
1
1
11
Clamp
1
1
0
0
12
Automatic
1
1
0
1
13
—
1
1
1
0
14
—
1
1
1
1
15
—
MOTOROLA
MC145740
9
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