AD6652BBC datasheet(62/76 Pages) AD

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AD6652

Rev. 0 | Page 62 of 76

individual magnitudes. When this bit is 1, then 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

floating-point output modes is used. If the number is too large

to represent with the output scale chosen, then the mantissas of

the I and Q data clip do not overflow.

Normally, the AD6652 determines the exponent value that

optimizes numerical accuracy. However, if Bit 6 is set, the value

stored in Bits 3–0 is used to s

consistent scaling and accura

redictable output ranges.

on.

cale the output. This ensures

cy during conditions that warrant

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

RCF data. The options are defined in the Table 27 and are

discussed further in the Output Port Control Registers secti

Table 27. Output Formats

Bit Value

Output Formatting 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

actor is equal to

+72.25 dB.

ld be set high. Then 16 bits of I

data can be read through the microport in either the 8 + 4,

0xA6: BIST Register for Q

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

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

tested in the system. See the User-Configurable Built-In Self-

Test (BIST) section for further details. The second function is to

provide access to the Q 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. Then 16 bits of Q

data can be read through the microport in either the 8 + 4,

12 + 4, 12-bit linear, or 16-bit linear output modes. This data

can come from either the formatted RCF output or the

CIC5 output.

This 20-bit register controls the number of outputs of the RCF

rmed.

utputs and then terminate. The loading

gine running. For details

lt-

to test the memories of the AD6652, if

gister

pped

RCF. The scale factor is used to scale the data when the output

format is in fixed-point mode or when the force exponent bit is

high. If Bits 3–0 are represented by RCF scale, the scaling facto

in dB is given by

Scale

RCF

Factor

Scaling

)

(

log

)

(

−

For an RCF scale of 0, the scaling factor is equal to −18.06 dB;

for a maximum RCF scale of 15, the scaling f

0xA5: BIST Register for I

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

complete functionality of the I datapath in the channel to be

tested in the system. See the User-Configurable Built-In Self-

Test (BIST) section for details. The second function is to

provide access to the I output data through the microport.

accomplish this, the Map RCF Data to BIST bit in the RCF

Control Register 2, 0xA9, shou

12 + 4, 12-bit linear, or 16-bit linear output modes. This data

can come from either the formatted RCF output or the

CIC5 output.

0xA7: BIST Outputs to Accumulate

or CIC filter that are observed when a BIST test is perfo

The BIST signature registers at Addresses 0xA5 and 0xA

observe this number of o

of this register also starts the BIST en

on utilizing the BIST circuitry, see the User-Configurable Bui

In Self-Test (BIST) section.

0xA8: RAM BIST Control Register

This 3-bit register is used

a failure is suspected. Bit 0 of this register is written with a

1 when the channel is in sleep mode. The user waits for

1600 CLKs, and then polls the bits. If Bit 1 is high, then the

CMEM failed the test; if Bit 2 is high, then the data memory

used by the RCF failed the test.

0xA9: Output Control Re

Bit 9 of this register allows the RCF or CIC5 data to be ma

to the BIST registers at Addresses 0xA5 and 0xA6. When this bit

is 0, then the BIST register is in signature mode and ready for a

self-test to be run. When this bit is 1, then the output data from

the RCF (after formatting) or from CIC5 data is mapped to

these registers and can be read through the microport.

Bit 5 determines the word length used by the parallel port. If

this bit is 0, then the parallel port uses 12-bit words for I and

If this bit is 1, then the parallel port uses 16-bit words for I a

Q. When the fixed-point output option is chosen from the RCF

control register, then these bits also set the rounding correctly i

the output formatter of the RCF.

Bits 4–0 are reserved and should be written low when

programming.

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