Sub-Audio Signaling Processor
Page 16 of 24
MX805A
5.2.5.2.1 Command Word P
Bits
15
LSB
14
13
12
P
LPF Bandwidth
0
0
0
0
0
0
1
0
0
1
1
1
1
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
2
300Hz
200Hz
150Hz
120Hz
100Hz
85.7Hz
75Hz
3
4
5
6
7
8
Table 9: Valid Values of P
Bits 12 to 15 are used to produce the data word “P” as shown in Table 9. The cutoff frequency f
point) of the TX Sub-Audio Lowpass filter is calculated as:
(0.5dB
C/O
fXTAL
32 x 208.33 x P
fC/O
=
fXTAL
32× 208.33× fC/O
P =
Table 9 is provided as and example and calculated using a Xtal/Clock (f
) frequency of 4.00MHz. As
XTAL
illustrated, only values of “P” of 2 to 8 are usable
5.2.5.2.2 Command Word Q
Bits 0 to 10 (See Figure 7) are used to produce the data word “Q” which sets one of the parameters described
below. As you can see, Command Word “Q” could be used to produce a parameter outside that specified in
the “Characteristics” section of this data bulletin. Care should be taken not to do this. Examples for limits of
“Q” in each operational configuration are included. “Q” = 0 is not valid in the following calculations. Bit 11 is
not used and must be set to logic “0”.
(a) CTCSS TX Tone Frequency (f
)
CTCSS OUT
fXTAL
32 x "Q"
f
=
=
67Hz
1866
CTCSS OUT
fCTCSS OUT
=
Hz
So “Q”
“11101001010”
“00111110100”
fXTAL
32 x fCTCSS OUT
f
=
=
250Hz
500
CTCSS OUT
so "Q" =
Hz
So “Q”
(b) NRZ TX Baud Rate (R
fXTAL
)
NRZ TX
R
=
=
67bps
1866
NRZ TX
RNRZ TZ
=
bits/sec
32 x "Q"
So “Q”
“11101001010”
“00110100001”
fXTAL
32 x RNRZ TZ
R
=
=
300bits/sec
417
NRZ TX
so "Q" =
So “Q”
(c) NRZ RX Baud Rate (R
fXTAL
)
NRZ RX
R
=
=
100bps
114
NRZ RX
RNRZRX
=
bits/sec
32 x11 x "Q"
So “Q”
“00001110010”
“00000100110”
fXTAL
352 x RNRZRX
R
=
=
300bits/sec
38
NRZ RX
so "Q" =
So “Q”
ã2001 MX-COM, Inc.
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Doc. # 20480116.006
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