AM79C30AVC datasheet(31/101 Pages) AMD

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Am79C30A/32A Data Sheet

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:

z = cos (wT) + i V sin(wT)

i = (–1)

1/2

w = frequency of input signal in Hz · 2pi

T = sample period in seconds (0.125 ms)

hj (j = 0,1,...7) = user-defined coefficients.

Each hj coefficient is defined by the following equation:

where each hj Coefficient Register pair has the follow-

ing format:

and Ai = –1 Si 2

–Mi , (i=0,1,2,3).

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-

Table 28.

Recommended Ranges

Recommended and guaranteed

0 to +12 dB plus infinite in 0.5 dB steps

GER

–10 to +18 dB plus infinite in 0.5 dB steps

–12 to 0 dB plus infinite in 0.5 dB steps

STG

–18 to 0 dB plus infinite in 0.5 dB steps

Table 29.

Design Ranges

Limits by design

–84.3 to 14.0 dB plus infinite in 0.1 dB steps

over most of the range

GER

–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

STG

–84.3 to 14.0 dB plus infinite in 0.1 dB steps

over most of the range

1 z

–

2 z

–

+++

–

7 z

–

A3 1

A2 1

A 1

()

[]

{}

Byte

6 5 4

2 1 0

LSB

MSB

Table 30.

X/R Filter Format

Byte

Value

h0 LSB

h0 MSB

h1 LSB

h2 LSB

h2 MSB

h3 LSB

h3 MSB

h4 LSB

h4 MSB

h5 LSB

h5 MSB

h6 LSB

h6 MSB

h7 LSB

h7 MSB

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