AD6634BCSLASHPCB datasheet(40/52 Pages) AD

40 / 52 page

REV. 0

–40–

AD6634

Bits 9–5 are the actual scale value used when the Level Indicator,

LI pin associated with this channel is active.

Bits 4–0 are the actual scale value used when the Level Indicator,

LI pin associated with this channel is active.

0x93:

Reserved (must be written Low).

0x94: CIC5 Decimation – 1 (MCIC5 – 1)

This register is used to set the decimation in the CIC5 filter.

The value written to this register is the decimation minus one.

Although this is an 8-bit register, the decimation is usually lim-

ited to between 1 and 32. Decimations higher than 32 would

require more scaling than the CIC5 is capable of.

0x95: CIC5 Scale

The CIC5 scale factor is used to compensate for the growth of

the CIC5 filter. Consult the CIC5 section for details.

0x96:

Reserved (must be written low).

0xA0: RCF Decimation – 1 (MRCF – 1)

This register is used to set the decimation of the RCF stage. The

value written is the decimation minus one. Although this is an

8-bit register that allows decimation up to 256, for most filtering

scenarios the decimation should be limited between 1 and 32.

Higher decimations are allowed but the alias protection of the

RCF may not be acceptable for some applications.

0xA1: RCF Decimation Phase (PRCF)

This register allows any one of the MRCF phases of the filter to

be used and can be adjusted dynamically. This phase is updated

each time a filter is started. When a channel is synchronized, it

will retain the phase setting chosen here. This can be used as

part of a timing recovery loop with an external processor or can

allow multiple RCFs to work together while using a single RCF

pair. The RCF section should be consulted for further details.

0xA2: RCF Number of Taps – 1 (NTAPS – 1)

The number of taps for the RCF filter minus one is written here.

0xA3: RCF Coefficient Offset (CORCF)

This register is used to specify which section of the 256-word

coefficient memory is used for a filter. It can be used to select

between multiple filters that are loaded into memory and refer-

enced by this pointer. This register is shadowed and the filter

pointer is updated every time a new filter is started. This allows

the coefficient offset to be written even while a filter is being

computed with disturbing operation. The next sample that

comes out of the RCF will be with the new filter.

0xA4: RCF Control Register

The RCF control register is an 11-bit register that controls the

general features of the RCF as well as the output formatting.

The bits of this register and their functions are described below.

Bit 10 bypasses the RCF filter and sends the CIC5 output data

to the BIST-I and BIST-Q registers. The 16 MSBs of the CIC5

data can be accessed from this register if Bit 9 of the RCF Control

Bit 9 of this register controls the source of the input data to the

RCF. If this bit is 0, the RCF processes the output data of its

own channel. If this bit is 1, it processes the data from the CIC5

of another channel. The CIC5 that the RCF is connected to

when this bit is 1 is shown in the Table XII. These can be

used to allow multiple RCFs to be used together to process

wider bandwidth channels. See the Multiprocessing section for

further details.

Table XII. RCF Input Configurations

Channel

RCF Input Source When Bit 9 is 1

Bit 8 is used as an extra address to allow a second block of 128

words of CMEM to be addressed by the channel addresses at

0x00–0x7F. If this bit is 0, the first 128 words are written; and if

this bit is 1, a second 128 words is written. This bit is only used

to program the coefficient memory. It is not used in any way by

the processing and filters longer than 128 taps can be performed.

Bit 7 is used to help control the output formatting of the AD6634s

RCF data. This bit is only used when the 8 + 4 or 12 + 4 floating-

point modes are chosen. These modes are enabled by Bits 5 and

4 of this register below. When this bit is 0, the I and Q output

exponents are determined separately based on their individual

magnitudes. When this bit is 1, the I and Q data is a complex

floating-point number where I and Q use a single exponent

that is determined based on the maximum magnitude of I or Q.

Bit 6 is used to force the Output Scale Factor in Bits 3–0 of this

point output modes is used. If the number was too large to

represent with the output scale chosen, the mantissas of the

Iand Q data clip and do not overflow.

Bits 5 and 4 choose the output formatting option used by the

RCF data. The options are defined in the Table XIII and are

discussed further in the Output Format section.

Table XIII. Output Formats

Bit Values

Output Option

12-Bit Mantissa and 4-Bit Exponent (12 + 4)

8-Bit Mantissa and 4-Bit Exponent (8 + 4)

Fixed-Point Mode

Bits 3–0 of this register represent the Output Scale Factor of the

RCF. It is used to scale the data when the output format is in

fixed-point mode or when the Force Exponent bit is high.

0xA5: BIST Register for I

This register serves two purposes. The first is to allow the complete

functionality of the I data path in the channel to be tested in the

system. The BIST section of the data sheet should be consulted

for further details. The second function is to provide access to the

I output data through the microport. To accomplish this, the

Map RCF data to BIST bit in the RCF Control register 2, 0xA9,

should be set high. Sixteen bits of I data can then be read through

the microport in either the 8 + 4, 12 + 4, 12-bit linear, or 16-bit

linear output modes. This data may come from either the formatted

RCF output or the CIC5 output.

0xA6: BIST Register for Q

This register serves two purposes. The first is to allow the complete

functionality of Q data path in the channel to be tested in the

system. The BIST section of the data sheet should be consulted

for further details. The second function is to provide access to

AD6634BC/PCB датащи(PDF) 40 Page - Analog Devices

AD6634BC/PCB датащи(HTML) 40 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

датащи скачать

ссылки URL