Texas Instruments Incorporated

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GC1012B 3.3V DIGITAL TUNER

SLWS138B

This document contains information which may be changed at any time without notice

3.3

FILTER MODE REGISTER

This register controls filtering, output formatting and the diagnostic input mode.

ADDRESS 5:

Filter Mode Register

BIT

TYPE

NAME

DESCRIPTION

0-2

R/W

DEC[0:2]

The decimation mode. The output sample rate is set using DEC according to the

following table:

DECCOMPLEX

REAL

(REAL = 0)

(REAL = 1)

?

3

R/W

-

Unused.

4

R/W

REAL

Output real samples instead of complex samples. The output spectrum is centered from

FLIP bit described below is active low in the real mode.

5

R/W

OFFSET

Offset the complex output spectrum. Used in the complex output mode (REAL=0) to

(see DEC above for the COMPLEX mode). This mode is useful for single-sideband AM

signals because it moves the lower band edge up to zero frequency where it belongs.

The upper half of the spectrum will appear as negative frequencies.

6

R/W

FLIP

Flip the output spectrum. This bit inverts the output spectrum. In the complex mode the

spectrum. In the real mode FLIP=0 flips the spectrum.

7

R/W

DIAG

Use the diagnostic ramp for the input to the chip instead of the X input. The ramp counts

from -2048 to +2047 and then starts over again.

The effect on the output spectrum of the REAL, OFFSET and FLIP bits is illustrated in the following

Figure 4. Output Spectral Formats

0

NORMAL (FLIP=0 OFFSET=0 REAL=0)

0

FLIPPED (FLIP=1)

0

OFFSET AND FLIPPED (FLIP=1 OFFSET=1)

0

REAL AND FLIPPED (FLIP=0 REAL=1)

0

OFFSET (OFFSET=1)

0

REAL MODE (REAL=1 FLIP=1)