RCVDL56DPFL/SP, RCV56DPFL/SP, and RCV336DPFL/SP Designer’s Guide
1119
4-19
The AGC may be disabled by first writing 0 to address 9BBh (DSRATE), then writing a 07FFh to address 8B9h (DUGAIN).
The first-order low pass filter in each level detector, defined by the coefficients LPGAIN and LPFBK, controls the response
time of each tone detector. Normally, these coefficients will not require alteration, but if, for example, a rapid cadence must
be detected on a tone, then the 3 dB cutoff is approximately the reciprocal of the on-time or off-time of the tone, whichever is
shorter. Decreasing LPFBK will speed up the response time. If LPFBK is decremented, then LPGAIN should be increase by
the same amount. The gain of the filter should be set to unity ( LPFBK Å 7FFFh). The default response time is in
the order of 0.01 seconds.
1026F4-6 Tone Det
Level
Detect
TONEB
Bit
Tone B
Detector
AGC
Level
Detect
TONEC
Bit
P
refilte
r
Squarer
Tone C
Detector
Level
Detect
TONEA
Bit
Tone A
Detector
Biquad 1
Biquad 2
+
ABS
x
RXA
x
Integrator
Fixed Gain
DAGCRF
(BBBh)
DUGAIN (8B9h)
DSRATE
(9BBh)
x
Figure 4-6. Tone Detectors
Table 4-4. TONEA, TONEB, and TONEC DSP RAM Addresses (Hex)
TONEA
TONEB
TONEC
Prefilter
Parameter
Biquad1
Biquad2
Biquad1
Biquad2
Biquad1
Biquad2
Biquad1
Biquad2
A3
AA1
BA1
AA7
BA7
AAD
BAD
AB2
BB2
A2
AA2
BA2
AA8
BA8
AAE
BAE
AB3
BB3
A1
AA3
BA3
AA9
BA9
AAF
BAF
AB4
BB4
B2
AA4
BA4
AAA
BAA
AB0
BB0
AB5
BB5
B1
AA5
BA5
AAB
BAB
AB1
BB1
AB6
BB6
Table 4-5. TONEA, TONEB, and TONEC Default Values (Hex)
TONEA
TONEB
TONEC
Parameter
Address
Value (Hex)
Address
Value (Hex)
Address
Value (Hex)
LPFBK
BA0
7F30
BA6
7E67
BAC
7F30
LPGAIN
AA0
00CF
AA6
02DF
AAC
00CF
THRESHU
AB8
0880
AB9
2A00
ABA
1600
THRESHL
BB8
0580
BB9
1C00
BBA
0A00
Содержание RC336DPFL
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