AM79C32A Advanced Micro Devices, AM79C32A Datasheet - Page 31

• Manufacturer Part Number: AM79C32A
• Description: Digital Subscriber Controller (DSC) Circuit
• Manufacturer: Advanced Micro Devices

As an example, in a hands-free application using an
electret requiring 24 dB of gain in the transmit path for
optimum performance. The typical implementation
would use 18 dB of GA and 6 dB of GX gain. The user
would then have a programmable range of +6 dB to –66
dB utilizing GX. Selection of these gain points is of
course, application specific, and will depend on the per-
formance requirements of the system.
Listings of the optimized programming values for vari-
ous levels are included in Appendix A. Values listed in
the recommended tables are still correct and will per-
form as stated. There is no need to convert to the ex-
tended values unless greater resolution is required.
Programmable Filter Coefficients and Equations
The frequency domain transfer function equation for
the X and R filters is:
where:
Each hj coefficient is defined by the following equation:
Recommended and guaranteed
GX
GER
GR
STG
Limits by design
GX
GER
GR
STG
z = cos (wT) + i V sin(wT)
i = (–1)
w = frequency of input signal in Hz · 2pi
T = sample period in seconds (0.125 ms)
hj (j = 0,1,...7) = user-defined coefficients.
h
Table 28. Recommended Ranges
f
=
0 to +12 dB plus infinite in 0.5 dB steps
–10 to +18 dB plus infinite in 0.5 dB steps
–12 to 0 dB plus infinite in 0.5 dB steps
–18 to 0 dB plus infinite in 0.5 dB steps
–84.3 to 14.0 dB plus infinite in 0.1 dB steps
over most of the range
–24.1 to 24.1 dB plus infinite in 0.1 dB steps
over most of the range
–84.3 to 14.0 dB plus infinite in 0.1 dB steps
over most of the range
–84.3 to 14.0 dB plus infinite in 0.1 dB steps
over most of the range
1/2
hj
h
h
Table 29. Design Ranges
0
5
=
z
+
–
h
5
A3 1
1
+
z
h
–
1
6
z
+
+
–
h
6
A2 1
2
+
z
h
–
2
7
+
z
+
–
A 1
h
7
3
z
–
+
3
A0
+
h
4
z
–
Am79C30A/32A Data Sheet
4
+
where each hj Coefficient Register pair has the follow-
ing format:
and Ai = –1 Si 2
The X and R filter coefficients are programmed using a
16-byte transfer with the format shown in Table 30.
Note:
AmMAP™ software, which calculates X and R filter coeffi-
cients, is available from Advanced Micro Devices. Contact
your local AMD Sales Office for more information.
Test Facilities
Three capabilities are provided for MAP operation ver-
ification.
MAP Analog Loopback
Signals sent in on AINA or AINB may be sent back out
to EAR1/EAR2 or LS1/LS2 by looping the MAP path in
the MUX. The MUX should be set up for Ba-to-Ba loop-
back by writing 33H to MCR1, MCR2, or MCR3. No
other MUX connections overriding Ba-to-Ba should be
programmed. This test allows the MAP analog and dig-
ital to be tested using a local signal source.
MAP Digital Loopback 1
This loopback mode connects the interpolator output to
the decimator input in place of the ADC output. This
mode allows verification from the S Interface or micro-
Byte
MSB
LSB
Byte
Table 30. X/R Filter Format
10
11
12
13
14
15
0
1
2
4
5
6
7
8
9
S1
S3
7
–Mi
, (i=0,1,2,3).
6 5 4
M1
M3
S0
S2
h0 MSB
h2 MSB
h3 MSB
h4 MSB
h5 MSB
h6 MSB
h7 MSB
h0 LSB
h1 LSB
h2 LSB
h3 LSB
h4 LSB
h5 LSB
h6 LSB
h7 LSB
3
Value
2 1 0
M0
M2
31